Merge pull request #1112 from TomHarte/VDPs

Clean up TMS9918-related code.
2024-11-18 17:06:15 +00:00 · 2023-01-10 13:40:47 -05:00 · 2023-01-10 13:40:47 -05:00 · dbff7592f5
commit dbff7592f5
parent 4eedec50fb 9085ba4081
16 changed files with 2284 additions and 1859 deletions
--- a/Analyser/Static/Sega/Target.hpp
+++ b/Analyser/Static/Sega/Target.hpp
@ -48,7 +48,9 @@ struct Target: public Analyser::Static::Target, public Reflection::StructImpl<Ta
 	}
 };

-#define is_master_system(v) v >= Analyser::Static::Sega::Target::Model::MasterSystem
+constexpr bool is_master_system(Analyser::Static::Sega::Target::Model model) {
+	return model >= Analyser::Static::Sega::Target::Model::MasterSystem;
+}

 }
 }
--- a/Components/9918/9918.cpp
+++ b/Components/9918/9918.cpp
--- a/Components/9918/9918.hpp
+++ b/Components/9918/9918.hpp
@ -12,13 +12,38 @@
 #include "../../Outputs/CRT/CRT.hpp"
 #include "../../ClockReceiver/ClockReceiver.hpp"

-#include "Implementation/9918Base.hpp"
-
 #include <cstdint>

 namespace TI {
 namespace TMS {

+enum Personality {
+	TMS9918A,	// includes the 9928 and 9929; set TV standard and output device as desired.
+	V9938,
+	V9958,
+
+	// Sega extensions.
+	SMSVDP,
+	SMS2VDP,
+	GGVDP,
+	MDVDP,
+};
+
+enum class TVStandard {
+	/*! i.e. 50Hz output at around 312.5 lines/field */
+	PAL,
+	/*! i.e. 60Hz output at around 262.5 lines/field */
+	NTSC
+};
+
+}
+}
+
+#include "Implementation/9918Base.hpp"
+
+namespace TI {
+namespace TMS {
+
 /*!
 	Provides emulation of the TMS9918a, TMS9928 and TMS9929. Likely in the future to be the
 	vessel for emulation of sufficiently close derivatives, such as the Master System VDP.
@ -30,13 +55,10 @@ namespace TMS {
 	These chips have only one non-on-demand interaction with the outside world: an interrupt line.
 	See get_time_until_interrupt and get_interrupt_line for asynchronous operation options.
 */
-class TMS9918: public Base {
+template <Personality personality> class TMS9918: private Base<personality> {
 	public:
-		/*!
-			Constructs an instance of the drive controller that behaves according to personality @c p.
-			@param p The type of controller to emulate.
-		*/
-		TMS9918(Personality p);
+		/*! Constructs an instance of the VDP that behaves according to the templated personality. */
+		TMS9918();

 		/*! Sets the TV standard for this TMS, if that is hard-coded in hardware. */
 		void set_tv_standard(TVStandard standard);
@ -44,18 +66,24 @@ class TMS9918: public Base {
 		/*! Sets the scan target this TMS will post content to. */
 		void set_scan_target(Outputs::Display::ScanTarget *);

-		/// Gets the current scan status.
+		/*! Gets the current scan status. */
 		Outputs::Display::ScanStatus get_scaled_scan_status() const;

-		/*! Sets the type of display the CRT will request. */
+		/*! Sets the type of CRT display. */
 		void set_display_type(Outputs::Display::DisplayType);

-		/*! Gets the type of display the CRT will request. */
+		/*! Gets the type of CRT display. */
 		Outputs::Display::DisplayType get_display_type() const;

 		/*!
-			Runs the VCP for the number of cycles indicate; it is an implicit assumption of the code
-			that the input clock rate is 3579545 Hz, the NTSC colour clock rate.
+			Runs the VDP for the number of cycles indicate; the input clock rate is implicitly assumed.
+
+			For everything except the Mega Drive VDP:
+				* the input clock rate should be 3579545 Hz, the NTSC colour clock rate.
+
+			For the Mega Drive:
+				* the input clock rate should be around 7.6MHz; 15/7ths of the NTSC colour
+				clock rate for NTSC output and 12/7ths of the PAL colour clock rate for PAL output.
 		*/
 		void run_for(const HalfCycles cycles);

@ -65,11 +93,11 @@ class TMS9918: public Base {
 		/*! Gets a register value. */
 		uint8_t read(int address);

-		/*! Gets the current scan line; provided by the Master System only. */
-		uint8_t get_current_line();
+		/*! Gets the current scan line; provided by the Sega VDPs only. */
+		uint8_t get_current_line() const;

-		/*! Gets the current latched horizontal counter; provided by the Master System only. */
-		uint8_t get_latched_horizontal_counter();
+		/*! Gets the current latched horizontal counter; provided by the Sega VDPs only. */
+		uint8_t get_latched_horizontal_counter() const;

 		/*! Latches the current horizontal counter. */
 		void latch_horizontal_counter();
@ -81,7 +109,7 @@ class TMS9918: public Base {
 			If get_interrupt_line is true now of if get_interrupt_line would
 			never return true, returns HalfCycles::max().
 		*/
-		HalfCycles get_next_sequence_point();
+		HalfCycles get_next_sequence_point() const;

 		/*!
 			Returns the amount of time until the nominated line interrupt position is
@ -96,7 +124,7 @@ class TMS9918: public Base {
 		/*!
 			@returns @c true if the interrupt line is currently active; @c false otherwise.
 		*/
-		bool get_interrupt_line();
+		bool get_interrupt_line() const;
 };

 }
--- a/Components/9918/Implementation/9918.cpp
+++ b/Components/9918/Implementation/9918.cpp
@ -0,0 +1,809 @@
+//
+//  9918.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 25/11/2017.
+//  Copyright 2017 Thomas Harte. All rights reserved.
+//
+
+#include "../9918.hpp"
+
+#include <cassert>
+#include <cstring>
+#include <cstdlib>
+#include "../../../Outputs/Log.hpp"
+
+using namespace TI::TMS;
+
+namespace {
+
+// 342 internal cycles are 228/227.5ths of a line, so 341.25 cycles should be a whole
+// line. Therefore multiply everything by four, but set line length to 1365 rather than 342*4 = 1368.
+constexpr unsigned int CRTCyclesPerLine = 1365;
+constexpr unsigned int CRTCyclesDivider = 4;
+
+}
+
+template <Personality personality>
+Base<personality>::Base() :
+	crt_(CRTCyclesPerLine, CRTCyclesDivider, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Red8Green8Blue8) {
+	// Unimaginatively, this class just passes RGB through to the shader. Investigation is needed
+	// into whether there's a more natural form. It feels unlikely given the diversity of chips modelled.
+
+	if constexpr (is_sega_vdp(personality)) {
+		mode_timing_.line_interrupt_position = 64;
+
+		mode_timing_.end_of_frame_interrupt_position.column = 63;
+		mode_timing_.end_of_frame_interrupt_position.row = 193;
+	}
+
+	// Establish that output is delayed after reading by `output_lag` cycles; start
+	// at a random position.
+	read_pointer_.row = rand() % 262;
+	read_pointer_.column = rand() % (Timing<personality>::CyclesPerLine - output_lag);
+	write_pointer_.row = read_pointer_.row;
+	write_pointer_.column = read_pointer_.column + output_lag;
+}
+
+template <Personality personality>
+TMS9918<personality>::TMS9918() {
+	this->crt_.set_display_type(Outputs::Display::DisplayType::RGB);
+	this->crt_.set_visible_area(Outputs::Display::Rect(0.07f, 0.0375f, 0.875f, 0.875f));
+
+	// The TMS remains in-phase with the NTSC colour clock; this is an empirical measurement
+	// intended to produce the correct relationship between the hard edges between pixels and
+	// the colour clock. It was eyeballed rather than derived from any knowledge of the TMS
+	// colour burst generator because I've yet to find any.
+	this->crt_.set_immediate_default_phase(0.85f);
+}
+
+template <Personality personality>
+void TMS9918<personality>::set_tv_standard(TVStandard standard) {
+	this->tv_standard_ = standard;
+	switch(standard) {
+		case TVStandard::PAL:
+			this->mode_timing_.total_lines = 313;
+			this->mode_timing_.first_vsync_line = 253;
+			this->crt_.set_new_display_type(CRTCyclesPerLine, Outputs::Display::Type::PAL50);
+		break;
+		default:
+			this->mode_timing_.total_lines = 262;
+			this->mode_timing_.first_vsync_line = 227;
+			this->crt_.set_new_display_type(CRTCyclesPerLine, Outputs::Display::Type::NTSC60);
+		break;
+	}
+}
+
+template <Personality personality>
+void TMS9918<personality>::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
+	this->crt_.set_scan_target(scan_target);
+}
+
+template <Personality personality>
+Outputs::Display::ScanStatus TMS9918<personality>::get_scaled_scan_status() const {
+	// The input was scaled by 3/4 to convert half cycles to internal ticks,
+	// so undo that and also allow for: (i) the multiply by 4 that it takes
+	// to reach the CRT; and (ii) the fact that the half-cycles value was scaled,
+	// and this should really reply in whole cycles.
+	return this->crt_.get_scaled_scan_status() * (4.0f / (3.0f * 8.0f));
+}
+
+template <Personality personality>
+void TMS9918<personality>::set_display_type(Outputs::Display::DisplayType display_type) {
+	this->crt_.set_display_type(display_type);
+}
+
+template <Personality personality>
+Outputs::Display::DisplayType TMS9918<personality>::get_display_type() const {
+	return this->crt_.get_display_type();
+}
+
+void LineBuffer::reset_sprite_collection() {
+	sprites_stopped = false;
+	active_sprite_slot = 0;
+
+	for(int c = 0; c < 8; ++c) {
+		active_sprites[c].shift_position = 0;
+	}
+}
+
+template <Personality personality>
+void Base<personality>::posit_sprite(LineBuffer &buffer, int sprite_number, int sprite_position, int screen_row) {
+	if(!(status_ & StatusSpriteOverflow)) {
+		status_ = uint8_t((status_ & ~0x1f) | (sprite_number & 0x1f));
+	}
+	if(buffer.sprites_stopped) return;
+
+	// A sprite Y of 208 means "don't scan the list any further".
+	if(mode_timing_.allow_sprite_terminator && sprite_position == mode_timing_.sprite_terminator) {
+		buffer.sprites_stopped = true;
+		return;
+	}
+
+	const int sprite_row = (((screen_row + 1) % mode_timing_.total_lines) - ((sprite_position + 1) & 255)) & 255;
+	if(sprite_row < 0 || sprite_row >= sprite_height_) return;
+
+	if(buffer.active_sprite_slot == mode_timing_.maximum_visible_sprites) {
+		status_ |= StatusSpriteOverflow;
+		return;
+	}
+
+	LineBuffer::ActiveSprite &sprite = buffer.active_sprites[buffer.active_sprite_slot];
+	sprite.index = sprite_number;
+	sprite.row = sprite_row >> (sprites_magnified_ ? 1 : 0);
+	++buffer.active_sprite_slot;
+}
+
+template <Personality personality>
+void TMS9918<personality>::run_for(const HalfCycles cycles) {
+	// As specific as I've been able to get:
+	// Scanline time is always 228 cycles.
+	// PAL output is 313 lines total. NTSC output is 262 lines total.
+	// Interrupt is signalled upon entering the lower border.
+
+	// Convert 456 clocked half cycles per line to 342 internal cycles per line;
+	// the internal clock is 1.5 times the nominal 3.579545 Mhz that I've advertised
+	// for this part. So multiply by three quarters.
+	const int int_cycles = this->clock_converter_.to_internal(cycles.as<int>());
+	if(!int_cycles) return;
+
+	// There are two intertwined processes here, 'writing' (which means writing to the
+	// line buffers, i.e. it's everything to do with collecting a line) and 'reading'
+	// (which means reading from the line buffers and generating video).
+	int write_cycles_pool = int_cycles;
+	int read_cycles_pool = int_cycles;
+
+	while(write_cycles_pool || read_cycles_pool) {
+#ifndef NDEBUG
+		LineBufferPointer backup = this->read_pointer_;
+#endif
+
+		if(write_cycles_pool) {
+			// Determine how much writing to do.
+			const int write_cycles = std::min(
+				Timing<personality>::CyclesPerLine - this->write_pointer_.column,
+				write_cycles_pool
+			);
+			const int end_column = this->write_pointer_.column + write_cycles;
+			LineBuffer &line_buffer = this->line_buffers_[this->write_pointer_.row];
+
+			// Determine what this does to any enqueued VRAM access.
+			this->minimum_access_column_ = this->write_pointer_.column + this->cycles_until_access_;
+			this->cycles_until_access_ -= write_cycles;
+
+
+			// ---------------------------------------
+			// Latch scrolling position, if necessary.
+			// ---------------------------------------
+			if constexpr (is_sega_vdp(personality)) {
+				if(this->write_pointer_.column < 61 && end_column >= 61) {
+					if(!this->write_pointer_.row) {
+						this->master_system_.latched_vertical_scroll = this->master_system_.vertical_scroll;
+
+						if(this->master_system_.mode4_enable) {
+							this->mode_timing_.pixel_lines = 192;
+							if(this->mode2_enable_ && this->mode1_enable_) this->mode_timing_.pixel_lines = 224;
+							if(this->mode2_enable_ && this->mode3_enable_) this->mode_timing_.pixel_lines = 240;
+
+							this->mode_timing_.allow_sprite_terminator = this->mode_timing_.pixel_lines == 192;
+							this->mode_timing_.first_vsync_line = (this->mode_timing_.total_lines + this->mode_timing_.pixel_lines) >> 1;
+
+							this->mode_timing_.end_of_frame_interrupt_position.row = this->mode_timing_.pixel_lines + 1;
+						}
+					}
+					line_buffer.latched_horizontal_scroll = this->master_system_.horizontal_scroll;
+				}
+			}
+
+
+
+			// ------------------------
+			// Perform memory accesses.
+			// ------------------------
+#define fetch(function, clock)																\
+	const int first_window = from_internal<personality, clock>(this->write_pointer_.column);\
+	const int final_window = from_internal<personality, clock>(end_column);					\
+	if(first_window == final_window) break;													\
+	if(final_window != clock_rate<personality, clock>()) {									\
+		function<true>(first_window, final_window);											\
+	} else {																				\
+		function<false>(first_window, final_window);										\
+	}
+
+			switch(line_buffer.line_mode) {
+				case LineMode::Text:		{	fetch(this->template fetch_tms_text, Clock::TMSMemoryWindow);		}	break;
+				case LineMode::Character:	{	fetch(this->template fetch_tms_character, Clock::TMSMemoryWindow);	}	break;
+				case LineMode::SMS:			{	fetch(this->template fetch_sms, Clock::TMSMemoryWindow);			}	break;
+				case LineMode::Refresh:		{	fetch(this->template fetch_tms_refresh, Clock::TMSMemoryWindow);	}	break;
+			}
+
+#undef fetch
+
+
+
+			// -------------------------------
+			// Check for interrupt conditions.
+			// -------------------------------
+			if(this->write_pointer_.column < this->mode_timing_.line_interrupt_position && end_column >= this->mode_timing_.line_interrupt_position) {
+				// The Sega VDP offers a decrementing counter for triggering line interrupts;
+				// it is reloaded either when it overflows or upon every non-pixel line after the first.
+				// It is otherwise decremented.
+				if constexpr (is_sega_vdp(personality)) {
+					if(this->write_pointer_.row >= 0 && this->write_pointer_.row <= this->mode_timing_.pixel_lines) {
+						--this->line_interrupt_counter;
+						if(this->line_interrupt_counter == 0xff) {
+							this->line_interrupt_pending_ = true;
+							this->line_interrupt_counter = this->line_interrupt_target;
+						}
+					} else {
+						this->line_interrupt_counter = this->line_interrupt_target;
+					}
+				}
+
+				// TODO: the V9938 provides line interrupts from direct specification of the target line.
+				// So life is easy.
+			}
+
+			if(
+				this->write_pointer_.row == this->mode_timing_.end_of_frame_interrupt_position.row &&
+				this->write_pointer_.column < this->mode_timing_.end_of_frame_interrupt_position.column &&
+				end_column >= this->mode_timing_.end_of_frame_interrupt_position.column
+			) {
+				this->status_ |= StatusInterrupt;
+			}
+
+
+
+			// -------------
+			// Advance time.
+			// -------------
+			this->write_pointer_.column = end_column;
+			write_cycles_pool -= write_cycles;
+
+			if(this->write_pointer_.column == Timing<personality>::CyclesPerLine) {
+				this->write_pointer_.column = 0;
+				this->write_pointer_.row = (this->write_pointer_.row + 1) % this->mode_timing_.total_lines;
+				LineBuffer &next_line_buffer = this->line_buffers_[this->write_pointer_.row];
+
+				// Establish the current screen output mode, which will be captured as a
+				// line mode momentarily.
+				this->screen_mode_ = this->current_screen_mode();
+
+				// Based on the output mode, pick a line mode.
+				next_line_buffer.first_pixel_output_column = Timing<personality>::FirstPixelCycle;
+				next_line_buffer.next_border_column = Timing<personality>::CyclesPerLine;
+				next_line_buffer.pixel_count = 256;
+				this->mode_timing_.maximum_visible_sprites = 4;
+				switch(this->screen_mode_) {
+					case ScreenMode::Text:
+						next_line_buffer.line_mode = LineMode::Text;
+						next_line_buffer.first_pixel_output_column = Timing<personality>::FirstTextCycle;
+						next_line_buffer.next_border_column = Timing<personality>::LastTextCycle;
+						next_line_buffer.pixel_count = 240;
+					break;
+					case ScreenMode::SMSMode4:
+						next_line_buffer.line_mode = LineMode::SMS;
+						this->mode_timing_.maximum_visible_sprites = 8;
+					break;
+					default:
+						next_line_buffer.line_mode = LineMode::Character;
+					break;
+				}
+
+				if(
+					(this->screen_mode_ == ScreenMode::Blank) ||
+					(this->write_pointer_.row >= this->mode_timing_.pixel_lines && this->write_pointer_.row != this->mode_timing_.total_lines-1))
+						next_line_buffer.line_mode = LineMode::Refresh;
+			}
+		}
+
+
+#ifndef NDEBUG
+		assert(backup.row == this->read_pointer_.row && backup.column == this->read_pointer_.column);
+		backup = this->write_pointer_;
+#endif
+
+
+		if(read_cycles_pool) {
+			// Determine how much time has passed in the remainder of this line, and proceed.
+			const int target_read_cycles = std::min(
+				Timing<personality>::CyclesPerLine - this->read_pointer_.column,
+				read_cycles_pool
+			);
+			int read_cycles_performed = 0;
+			uint32_t next_cram_value = 0;
+
+			while(read_cycles_performed < target_read_cycles) {
+				int read_cycles = target_read_cycles - read_cycles_performed;
+				if(!read_cycles) continue;
+
+				// Grab the next CRAM dot value and schedule a break in output if applicable.
+				const uint32_t cram_value = next_cram_value;
+				if constexpr (is_sega_vdp(personality)) {
+					next_cram_value = 0;
+
+					if(!this->upcoming_cram_dots_.empty() && this->upcoming_cram_dots_.front().location.row == this->read_pointer_.row) {
+						int time_until_dot = this->upcoming_cram_dots_.front().location.column - this->read_pointer_.column;
+
+						if(time_until_dot < read_cycles) {
+							read_cycles = time_until_dot;
+							next_cram_value = this->upcoming_cram_dots_.front().value;
+							this->upcoming_cram_dots_.erase(this->upcoming_cram_dots_.begin());
+						}
+					}
+				}
+
+				read_cycles_performed += read_cycles;
+
+				const int end_column = this->read_pointer_.column + read_cycles;
+				LineBuffer &line_buffer = this->line_buffers_[this->read_pointer_.row];
+
+
+				// --------------------
+				// Output video stream.
+				// --------------------
+
+#define crt_convert(action, time)		this->crt_.action(from_internal<personality, Clock::CRT>(time))
+#define output_sync(x)					crt_convert(output_sync, x)
+#define output_blank(x)					crt_convert(output_blank, x)
+#define output_default_colour_burst(x)	crt_convert(output_default_colour_burst, x)
+
+#define intersect(left, right, code)	{	\
+		const int start = std::max(this->read_pointer_.column, left);	\
+		const int end = std::min(end_column, right);	\
+		if(end > start) {\
+			code;\
+		}\
+	}
+
+#define border(left, right)	intersect(left, right, this->output_border(end - start, cram_value))
+
+				if(line_buffer.line_mode == LineMode::Refresh || this->read_pointer_.row > this->mode_timing_.pixel_lines) {
+					if(
+						this->read_pointer_.row >= this->mode_timing_.first_vsync_line &&
+						this->read_pointer_.row < this->mode_timing_.first_vsync_line + 4
+					) {
+						// Vertical sync.
+						// TODO: the Mega Drive supports interlaced video, I think?
+						if(end_column == Timing<personality>::CyclesPerLine) {
+							output_sync(Timing<personality>::CyclesPerLine);
+						}
+					} else {
+						// Right border.
+						border(0, Timing<personality>::EndOfRightBorder);
+
+						// Blanking region: output the entire sequence when the cursor
+						// crosses the start-of-border point.
+						if(
+							this->read_pointer_.column < Timing<personality>::StartOfLeftBorder &&
+							end_column >= Timing<personality>::StartOfLeftBorder
+						) {
+							output_blank(Timing<personality>::StartOfSync - Timing<personality>::EndOfRightBorder);
+							output_sync(Timing<personality>::EndOfSync - Timing<personality>::StartOfSync);
+							output_blank(Timing<personality>::StartOfColourBurst - Timing<personality>::EndOfSync);
+							output_default_colour_burst(Timing<personality>::EndOfColourBurst - Timing<personality>::StartOfColourBurst);
+							output_blank(Timing<personality>::StartOfLeftBorder - Timing<personality>::EndOfColourBurst);
+						}
+
+						// Border colour for the rest of the line.
+						border(Timing<personality>::StartOfLeftBorder, Timing<personality>::CyclesPerLine);
+					}
+				} else {
+					// Right border.
+					border(0, Timing<personality>::EndOfRightBorder);
+
+					// Blanking region.
+					if(
+						this->read_pointer_.column < Timing<personality>::StartOfLeftBorder &&
+						end_column >= Timing<personality>::StartOfLeftBorder
+					) {
+						output_blank(Timing<personality>::StartOfSync - Timing<personality>::EndOfRightBorder);
+						output_sync(Timing<personality>::EndOfSync - Timing<personality>::StartOfSync);
+						output_blank(Timing<personality>::StartOfColourBurst - Timing<personality>::EndOfSync);
+						output_default_colour_burst(Timing<personality>::EndOfColourBurst - Timing<personality>::StartOfColourBurst);
+						output_blank(Timing<personality>::StartOfLeftBorder - Timing<personality>::EndOfColourBurst);
+					}
+
+					// Left border.
+					border(Timing<personality>::StartOfLeftBorder, line_buffer.first_pixel_output_column);
+
+#define draw(function, clock) {																				\
+	const int relative_start = from_internal<personality, clock>(start - line_buffer.first_pixel_output_column);	\
+	const int relative_end = from_internal<personality, clock>(end - line_buffer.first_pixel_output_column);		\
+	if(relative_start == relative_end) break;																	\
+	this->function; }
+
+					// Pixel region.
+					intersect(
+						line_buffer.first_pixel_output_column,
+						line_buffer.next_border_column,
+						if(!this->asked_for_write_area_) {
+							this->asked_for_write_area_ = true;
+
+							this->pixel_origin_ = this->pixel_target_ = reinterpret_cast<uint32_t *>(
+								this->crt_.begin_data(line_buffer.pixel_count)
+							);
+						}
+
+						if(this->pixel_target_) {
+							switch(line_buffer.line_mode) {
+								case LineMode::SMS:			draw(draw_sms(relative_start, relative_end, cram_value), Clock::TMSPixel);	break;
+								case LineMode::Character:	draw(draw_tms_character(relative_start, relative_end), Clock::TMSPixel);	break;
+								case LineMode::Text:		draw(draw_tms_text(relative_start, relative_end), Clock::TMSPixel);			break;
+
+								case LineMode::Refresh:		break;	/* Dealt with elsewhere. */
+							}
+						}
+
+						if(end == line_buffer.next_border_column) {
+							const int length = line_buffer.next_border_column - line_buffer.first_pixel_output_column;
+							this->crt_.output_data(from_internal<personality, Clock::CRT>(length), line_buffer.pixel_count);
+							this->pixel_origin_ = this->pixel_target_ = nullptr;
+							this->asked_for_write_area_ = false;
+						}
+					);
+
+#undef draw
+
+					// Additional right border, if called for.
+					if(line_buffer.next_border_column != Timing<personality>::CyclesPerLine) {
+						border(line_buffer.next_border_column, Timing<personality>::CyclesPerLine);
+					}
+				}
+
+#undef border
+#undef intersect
+
+#undef crt_convert
+#undef output_sync
+#undef output_blank
+#undef output_default_colour_burst
+
+
+
+				// -------------
+				// Advance time.
+				// -------------
+				this->read_pointer_.column = end_column;
+			}
+
+			read_cycles_pool -= target_read_cycles;
+			if(this->read_pointer_.column == Timing<personality>::CyclesPerLine) {
+				this->read_pointer_.column = 0;
+				this->read_pointer_.row = (this->read_pointer_.row + 1) % this->mode_timing_.total_lines;
+			}
+		}
+
+		assert(backup.row == this->write_pointer_.row && backup.column == this->write_pointer_.column);
+	}
+}
+
+template <Personality personality>
+void Base<personality>::output_border(int cycles, [[maybe_unused]] uint32_t cram_dot) {
+	cycles = from_internal<personality, Clock::CRT>(cycles);
+	const uint32_t border_colour =
+		is_sega_vdp(personality) ?
+			master_system_.colour_ram[16 + background_colour_] :
+			palette[background_colour_];
+
+	if constexpr (is_sega_vdp(personality)) {
+		if(cram_dot) {
+			uint32_t *const pixel_target = reinterpret_cast<uint32_t *>(crt_.begin_data(1));
+			if(pixel_target) {
+				*pixel_target = border_colour | cram_dot;
+			}
+
+			// Four CRT cycles is one pixel width, so this doesn't need clock conversion.
+			// TODO: on the Mega Drive it may be only 3 colour cycles, depending on mode.
+			crt_.output_level(4);
+			cycles -= 4;
+		}
+	}
+
+	if(!cycles) {
+		return;
+	}
+
+	// If the border colour is 0, that can be communicated
+	// more efficiently as an explicit blank.
+	if(border_colour) {
+		uint32_t *const pixel_target = reinterpret_cast<uint32_t *>(crt_.begin_data(1));
+		if(pixel_target) {
+			*pixel_target = border_colour;
+		}
+		crt_.output_level(cycles);
+	} else {
+		crt_.output_blank(cycles);
+	}
+}
+
+template <Personality personality>
+void TMS9918<personality>::write(int address, uint8_t value) {
+	// Writes to address 0 are writes to the video RAM. Store
+	// the value and return.
+	if(!(address & 1)) {
+		this->write_phase_ = false;
+
+		// Enqueue the write to occur at the next available slot.
+		this->read_ahead_buffer_ = value;
+		this->queued_access_ = MemoryAccess::Write;
+		this->cycles_until_access_ = Timing<personality>::VRAMAccessDelay;
+
+		return;
+	}
+
+	// Writes to address 1 are performed in pairs; if this is the
+	// low byte of a value, store it and wait for the high byte.
+	if(!this->write_phase_) {
+		this->low_write_ = value;
+		this->write_phase_ = true;
+
+		// The initial write should half update the access pointer.
+		this->ram_pointer_ = (this->ram_pointer_ & 0xff00) | this->low_write_;
+		return;
+	}
+
+	// The RAM pointer is always set on a second write, regardless of
+	// whether the caller is intending to enqueue a VDP operation.
+	this->ram_pointer_ = (this->ram_pointer_ & 0x00ff) | uint16_t(value << 8);
+
+	this->write_phase_ = false;
+	if(value & 0x80) {
+		if constexpr (is_sega_vdp(personality)) {
+			if(value & 0x40) {
+				this->master_system_.cram_is_selected = true;
+				return;
+			}
+			value &= 0xf;
+		} else {
+			value &= 0x7;
+		}
+
+		// This is a write to a register.
+		switch(value) {
+			case 0:
+				if constexpr (is_sega_vdp(personality)) {
+					this->master_system_.vertical_scroll_lock = this->low_write_ & 0x80;
+					this->master_system_.horizontal_scroll_lock = this->low_write_ & 0x40;
+					this->master_system_.hide_left_column = this->low_write_ & 0x20;
+					this->enable_line_interrupts_ = this->low_write_ & 0x10;
+					this->master_system_.shift_sprites_8px_left = this->low_write_ & 0x08;
+					this->master_system_.mode4_enable = this->low_write_ & 0x04;
+				}
+				this->mode2_enable_ = this->low_write_ & 0x02;
+			break;
+
+			case 1:
+				this->blank_display_ = !(this->low_write_ & 0x40);
+				this->generate_interrupts_ = this->low_write_ & 0x20;
+				this->mode1_enable_ = this->low_write_ & 0x10;
+				this->mode3_enable_ = this->low_write_ & 0x08;
+				this->sprites_16x16_ = this->low_write_ & 0x02;
+				this->sprites_magnified_ = this->low_write_ & 0x01;
+
+				this->sprite_height_ = 8;
+				if(this->sprites_16x16_) this->sprite_height_ <<= 1;
+				if(this->sprites_magnified_) this->sprite_height_ <<= 1;
+			break;
+
+			case 2:
+				this->pattern_name_address_ = size_t((this->low_write_ & 0xf) << 10) | 0x3ff;
+				this->master_system_.pattern_name_address = this->pattern_name_address_ | ((personality == TMS::SMSVDP) ? 0x000 : 0x400);
+			break;
+
+			case 3:
+				this->colour_table_address_ = size_t(this->low_write_ << 6) | 0x3f;
+			break;
+
+			case 4:
+				this->pattern_generator_table_address_ = size_t((this->low_write_ & 0x07) << 11) | 0x7ff;
+			break;
+
+			case 5:
+				this->sprite_attribute_table_address_ = size_t((this->low_write_ & 0x7f) << 7) | 0x7f;
+				this->master_system_.sprite_attribute_table_address = this->sprite_attribute_table_address_ | ((personality == TMS::SMSVDP) ? 0x00 : 0x80);
+			break;
+
+			case 6:
+				this->sprite_generator_table_address_ = size_t((this->low_write_ & 0x07) << 11) | 0x7ff;
+				this->master_system_.sprite_generator_table_address = this->sprite_generator_table_address_ | ((personality == TMS::SMSVDP) ? 0x0000 : 0x1800);
+			break;
+
+			case 7:
+				this->text_colour_ = this->low_write_ >> 4;
+				this->background_colour_ = this->low_write_ & 0xf;
+			break;
+
+			case 8:
+				if constexpr (is_sega_vdp(personality)) {
+					this->master_system_.horizontal_scroll = this->low_write_;
+				}
+			break;
+
+			case 9:
+				if constexpr (is_sega_vdp(personality)) {
+					this->master_system_.vertical_scroll = this->low_write_;
+				}
+			break;
+
+			case 10:
+				if constexpr (is_sega_vdp(personality)) {
+					this->line_interrupt_target = this->low_write_;
+				}
+			break;
+
+			default:
+				LOG("Unknown TMS write: " << int(this->low_write_) << " to " << int(value));
+			break;
+		}
+	} else {
+		// This is an access via the RAM pointer.
+		if(!(value & 0x40)) {
+			// A read request is enqueued upon setting the address; conversely a write
+			// won't be enqueued unless and until some actual data is supplied.
+			this->queued_access_ = MemoryAccess::Read;
+			this->cycles_until_access_ = Timing<personality>::VRAMAccessDelay;
+		}
+		this->master_system_.cram_is_selected = false;
+	}
+}
+
+template <Personality personality>
+uint8_t TMS9918<personality>::get_current_line() const {
+	// Determine the row to return.
+	constexpr int row_change_position = 63;	// This is the proper Master System value; substitute if any other VDPs turn out to have this functionality.
+	int source_row =
+		(this->write_pointer_.column < row_change_position)
+			? (this->write_pointer_.row + this->mode_timing_.total_lines - 1) % this->mode_timing_.total_lines
+			: this->write_pointer_.row;
+
+	if(this->tv_standard_ == TVStandard::NTSC) {
+		if(this->mode_timing_.pixel_lines == 240) {
+			// NTSC 256x240:	00-FF, 00-06
+		} else if(this->mode_timing_.pixel_lines == 224) {
+			// NTSC 256x224:	00-EA, E5-FF
+			if(source_row >= 0xeb) source_row -= 6;
+		} else {
+			// NTSC 256x192:	00-DA, D5-FF
+			if(source_row >= 0xdb) source_row -= 6;
+		}
+	} else {
+		if(this->mode_timing_.pixel_lines == 240) {
+			// PAL 256x240:		00-FF, 00-0A, D2-FF
+			if(source_row >= 267) source_row -= 0x39;
+		} else if(this->mode_timing_.pixel_lines == 224) {
+			// PAL 256x224:		00-FF, 00-02, CA-FF
+			if(source_row >= 259) source_row -= 0x39;
+		} else {
+			// PAL 256x192:		00-F2, BA-FF
+			if(source_row >= 0xf3) source_row -= 0x39;
+		}
+	}
+
+	return uint8_t(source_row);
+}
+
+template <Personality personality>
+uint8_t TMS9918<personality>::read(int address) {
+	this->write_phase_ = false;
+
+	// Reads from address 0 read video RAM, via the read-ahead buffer.
+	if(!(address & 1)) {
+		// Enqueue the write to occur at the next available slot.
+		const uint8_t result = this->read_ahead_buffer_;
+		this->queued_access_ = MemoryAccess::Read;
+		return result;
+	}
+
+	// Reads from address 1 get the status register.
+	const uint8_t result = this->status_;
+	this->status_ &= ~(StatusInterrupt | StatusSpriteOverflow | StatusSpriteCollision);
+	this->line_interrupt_pending_ = false;
+	return result;
+}
+
+template <Personality personality>
+HalfCycles TMS9918<personality>::get_next_sequence_point() const {
+	if(!this->generate_interrupts_ && !this->enable_line_interrupts_) return HalfCycles::max();
+	if(get_interrupt_line()) return HalfCycles::max();
+
+	// Calculate the amount of time until the next end-of-frame interrupt.
+	const int frame_length = Timing<personality>::CyclesPerLine * this->mode_timing_.total_lines;
+	int time_until_frame_interrupt =
+		(
+			((this->mode_timing_.end_of_frame_interrupt_position.row * Timing<personality>::CyclesPerLine) + this->mode_timing_.end_of_frame_interrupt_position.column + frame_length) -
+			((this->write_pointer_.row * Timing<personality>::CyclesPerLine) + this->write_pointer_.column)
+		) % frame_length;
+	if(!time_until_frame_interrupt) time_until_frame_interrupt = frame_length;
+
+	if(!this->enable_line_interrupts_) {
+		return this->clock_converter_.half_cycles_before_internal_cycles(time_until_frame_interrupt);
+	}
+
+	// Calculate when the next line interrupt will occur.
+	int next_line_interrupt_row = -1;
+
+	int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->write_pointer_.column;
+	int line_of_next_interrupt_threshold = this->write_pointer_.row;
+	if(cycles_to_next_interrupt_threshold <= 0) {
+		cycles_to_next_interrupt_threshold += Timing<personality>::CyclesPerLine;
+		++line_of_next_interrupt_threshold;
+	}
+
+	if constexpr (is_sega_vdp(personality)) {
+		// If there is still time for a line interrupt this frame, that'll be it;
+		// otherwise it'll be on the next frame, supposing there's ever time for
+		// it at all.
+		if(line_of_next_interrupt_threshold + this->line_interrupt_counter <= this->mode_timing_.pixel_lines) {
+			next_line_interrupt_row = line_of_next_interrupt_threshold + this->line_interrupt_counter;
+		} else {
+			if(this->line_interrupt_target <= this->mode_timing_.pixel_lines)
+				next_line_interrupt_row = this->mode_timing_.total_lines + this->line_interrupt_target;
+		}
+	}
+
+	// If there's actually no interrupt upcoming, despite being enabled, either return
+	// the frame end interrupt or no interrupt pending as appropriate.
+	if(next_line_interrupt_row == -1) {
+		return this->generate_interrupts_ ?
+			this->clock_converter_.half_cycles_before_internal_cycles(time_until_frame_interrupt) :
+			HalfCycles::max();
+	}
+
+	// Figure out the number of internal cycles until the next line interrupt, which is the amount
+	// of time to the next tick over and then next_line_interrupt_row - row_ lines further.
+	const int local_cycles_until_line_interrupt = cycles_to_next_interrupt_threshold + (next_line_interrupt_row - line_of_next_interrupt_threshold) * Timing<personality>::CyclesPerLine;
+	if(!this->generate_interrupts_) return this->clock_converter_.half_cycles_before_internal_cycles(local_cycles_until_line_interrupt);
+
+	// Return whichever interrupt is closer.
+	return this->clock_converter_.half_cycles_before_internal_cycles(std::min(local_cycles_until_line_interrupt, time_until_frame_interrupt));
+}
+
+template <Personality personality>
+HalfCycles TMS9918<personality>::get_time_until_line(int line) {
+	if(line < 0) line += this->mode_timing_.total_lines;
+
+	int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->write_pointer_.column;
+	int line_of_next_interrupt_threshold = this->write_pointer_.row;
+	if(cycles_to_next_interrupt_threshold <= 0) {
+		cycles_to_next_interrupt_threshold += Timing<personality>::CyclesPerLine;
+		++line_of_next_interrupt_threshold;
+	}
+
+	if(line_of_next_interrupt_threshold > line) {
+		line += this->mode_timing_.total_lines;
+	}
+
+	return this->clock_converter_.half_cycles_before_internal_cycles(cycles_to_next_interrupt_threshold + (line - line_of_next_interrupt_threshold)*Timing<personality>::CyclesPerLine);
+}
+
+template <Personality personality>
+bool TMS9918<personality>::get_interrupt_line() const {
+	return
+		((this->status_ & StatusInterrupt) && this->generate_interrupts_) ||
+		(this->enable_line_interrupts_ && this->line_interrupt_pending_);
+}
+
+// TODO: [potentially] remove Master System timing assumptions in latch and get_latched below.
+template <Personality personality>uint8_t TMS9918<personality>::get_latched_horizontal_counter() const {
+	// Translate from internal numbering, which puts pixel output
+	// in the final 256 pixels of 342, to the public numbering,
+	// which counts the 256 pixels as items 0–255, starts
+	// counting at -48, and returns only the top 8 bits of the number.
+	int public_counter = this->latched_column_ - (342 - 256);
+	if(public_counter < -46) public_counter += 342;
+	return uint8_t(public_counter >> 1);
+}
+
+template <Personality personality>
+void TMS9918<personality>::latch_horizontal_counter() {
+	this->latched_column_ = this->write_pointer_.column;
+}
+
+template class TI::TMS::TMS9918<Personality::TMS9918A>;
+template class TI::TMS::TMS9918<Personality::V9938>;
+template class TI::TMS::TMS9918<Personality::V9958>;
+template class TI::TMS::TMS9918<Personality::SMSVDP>;
+template class TI::TMS::TMS9918<Personality::SMS2VDP>;
+template class TI::TMS::TMS9918<Personality::GGVDP>;
+template class TI::TMS::TMS9918<Personality::MDVDP>;
--- a/Components/9918/Implementation/9918Base.hpp
+++ b/Components/9918/Implementation/9918Base.hpp
--- a/Components/9918/Implementation/ClockConverter.hpp
+++ b/Components/9918/Implementation/ClockConverter.hpp
@ -0,0 +1,180 @@
+//
+//  ClockConverter.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 01/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef ClockConverter_hpp
+#define ClockConverter_hpp
+
+#include "../9918.hpp"
+#include "PersonalityTraits.hpp"
+
+namespace TI {
+namespace TMS {
+
+enum class Clock {
+	Internal,
+	TMSPixel,
+	TMSMemoryWindow,
+	CRT
+};
+
+template <Personality personality, Clock clk> constexpr int clock_rate() {
+	static_assert(
+		is_classic_vdp(personality) ||
+		is_yamaha_vdp(personality) ||
+		(personality == Personality::MDVDP)
+	);
+
+	switch(clk) {
+		case Clock::TMSPixel:			return 342;
+		case Clock::TMSMemoryWindow:	return 171;
+		case Clock::CRT:				return 1368;
+		case Clock::Internal:
+			if constexpr (is_classic_vdp(personality)) {
+				return 342;
+			} else if constexpr (is_yamaha_vdp(personality)) {
+				return 1368;
+			} else if constexpr (personality == Personality::MDVDP) {
+				return 3420;
+			}
+	}
+}
+
+template <Personality personality, Clock clock> constexpr int to_internal(int length) {
+	return length * clock_rate<personality, Clock::Internal>() / clock_rate<personality, clock>();
+}
+
+template <Personality personality, Clock clock> constexpr int from_internal(int length) {
+	return length * clock_rate<personality, clock>() / clock_rate<personality, Clock::Internal>();
+}
+
+/// Provides default timing measurements that duplicate the layout of a TMS9928's line,
+/// scaled to the clock rate specified.
+template <Personality personality> struct StandardTiming {
+	/// The total number of internal cycles per line of output.
+	constexpr static int CyclesPerLine = clock_rate<personality, Clock::Internal>();
+
+	/// The number of internal cycles that must elapse between a request to read or write and
+	/// it becoming a candidate for action.
+	constexpr static int VRAMAccessDelay = 6;
+
+	/// The first internal cycle at which pixels will be output in any mode other than text.
+	/// Pixels implicitly run from here to the end of the line.
+	constexpr static int FirstPixelCycle = 86 * CyclesPerLine / 342;
+
+	/// The first internal cycle at which pixels will be output text mode.
+	constexpr static int FirstTextCycle = 94 * CyclesPerLine / 342;
+
+	/// The final internal cycle at which pixels will be output text mode.
+	constexpr static int LastTextCycle = 334 * CyclesPerLine / 342;
+
+	// For the below, the fixed portion of line layout is:
+	//
+	//	[0, EndOfRightBorder):					right border colour
+	//	[EndOfRightBorder, StartOfSync):		blank
+	//	[StartOfSync, EndOfSync):				sync
+	//	[EndOfSync, StartOfColourBurst):		blank
+	//	[StartOfColourBurst, EndOfColourBurst):	the colour burst
+	//	[EndOfColourBurst, StartOfLeftBorder):	blank
+	//
+	// The region from StartOfLeftBorder until the end is then filled with
+	// some combination of pixels and more border, depending on the vertical
+	// position of this line and the current screen mode.
+	constexpr static int EndOfRightBorder	= 15 * CyclesPerLine / 342;
+	constexpr static int StartOfSync		= 23 * CyclesPerLine / 342;
+	constexpr static int EndOfSync			= 49 * CyclesPerLine / 342;
+	constexpr static int StartOfColourBurst	= 51 * CyclesPerLine / 342;
+	constexpr static int EndOfColourBurst	= 65 * CyclesPerLine / 342;
+	constexpr static int StartOfLeftBorder	= 73 * CyclesPerLine / 342;
+};
+
+/// Provides concrete, specific timing for the nominated personality.
+template <Personality personality> struct Timing: public StandardTiming<personality> {};
+
+/*!
+	Provides a [potentially-]stateful conversion between the external and internal clocks.
+	Unlike the other clock conversions, this one may be non-integral, requiring that
+	an error term be tracked.
+*/
+template <Personality personality> class ClockConverter {
+	public:
+		/*!
+			Given that another @c source external **half-cycles** has occurred,
+			indicates how many complete internal **cycles** have additionally elapsed
+			since the last call to @c to_internal.
+
+			E.g. for the TMS, @c source will count 456 ticks per line, and the internal clock
+			runs at 342 ticks per line, so the proper conversion is to multiply by 3/4.
+		*/
+		int to_internal(int source) {
+			switch(personality) {
+				// Default behaviour is to apply a multiplication by 3/4;
+				// this is correct for the TMS and Sega VDPs other than the Mega Drive.
+				default: {
+					const int result = source * 3 + cycles_error_;
+					cycles_error_ = result & 3;
+					return result >> 2;
+				}
+
+				// The two Yamaha chips have an internal clock that is four times
+				// as fast as the TMS, therefore a stateless translation is possible.
+				case Personality::V9938:
+				case Personality::V9958:
+				return source * 3;
+
+				// The Mega Drive runs at 3420 master clocks per line, which is then
+				// divided by 4 or 5 depending on other state. That's 7 times the
+				// rate provided to the CPU; given that the input is in half-cycles
+				// the proper multiplier is therefore 3.5.
+				case Personality::MDVDP: {
+					const int result = source * 7 + cycles_error_;
+					cycles_error_ = result & 1;
+					return result >> 1;
+				}
+			}
+		}
+
+		/*!
+			Provides the number of external cycles that need to begin from now in order to
+			get at least @c internal_cycles into the future.
+		*/
+		HalfCycles half_cycles_before_internal_cycles(int internal_cycles) const {
+			// Logic here correlates with multipliers as per @c to_internal.
+			switch(personality) {
+				default:
+					// Relative to the external clock multiplied by 3, it will definitely take this
+					// many cycles to complete a further (internal_cycles - 1) after the current one.
+					internal_cycles = (internal_cycles - 1) << 2;
+
+					// It will also be necessary to complete the current one.
+					internal_cycles += 4 - cycles_error_;
+
+					// Round up to get the first external cycle after
+					// the number of internal_cycles has elapsed.
+					return HalfCycles((internal_cycles + 2) / 3);
+
+				case Personality::V9938:
+				case Personality::V9958:
+					return HalfCycles((internal_cycles + 2) / 3);
+
+				case Personality::MDVDP:
+					internal_cycles = (internal_cycles - 1) << 1;
+					internal_cycles += 2 - cycles_error_;
+					return HalfCycles((internal_cycles + 6) / 7);
+			}
+		}
+
+	private:
+		// Holds current residue in conversion from the external to
+		// internal clock.
+		int cycles_error_ = 0;
+};
+
+}
+}
+
+#endif /* ClockConverter_hpp */
--- a/Components/9918/Implementation/Draw.hpp
+++ b/Components/9918/Implementation/Draw.hpp
@ -0,0 +1,293 @@
+//
+//  Draw.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 05/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef Draw_hpp
+#define Draw_hpp
+
+// MARK: - TMS9918
+
+template <Personality personality>
+void Base<personality>::draw_tms_character(int start, int end) {
+	LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
+
+	// Paint the background tiles.
+	const int pixels_left = end - start;
+	if(this->screen_mode_ == ScreenMode::MultiColour) {
+		for(int c = start; c < end; ++c) {
+			pixel_target_[c] = palette[
+				(line_buffer.patterns[c >> 3][0] >> (((c & 4)^4))) & 15
+			];
+		}
+	} else {
+		const int shift = start & 7;
+		int byte_column = start >> 3;
+
+		int length = std::min(pixels_left, 8 - shift);
+
+		int pattern = Numeric::bit_reverse(line_buffer.patterns[byte_column][0]) >> shift;
+		uint8_t colour = line_buffer.patterns[byte_column][1];
+		uint32_t colours[2] = {
+			palette[(colour & 15) ? (colour & 15) : background_colour_],
+			palette[(colour >> 4) ? (colour >> 4) : background_colour_]
+		};
+
+		int background_pixels_left = pixels_left;
+		while(true) {
+			background_pixels_left -= length;
+			for(int c = 0; c < length; ++c) {
+				pixel_target_[c] = colours[pattern&0x01];
+				pattern >>= 1;
+			}
+			pixel_target_ += length;
+
+			if(!background_pixels_left) break;
+			length = std::min(8, background_pixels_left);
+			byte_column++;
+
+			pattern = Numeric::bit_reverse(line_buffer.patterns[byte_column][0]);
+			colour = line_buffer.patterns[byte_column][1];
+			colours[0] = palette[(colour & 15) ? (colour & 15) : background_colour_];
+			colours[1] = palette[(colour >> 4) ? (colour >> 4) : background_colour_];
+		}
+	}
+
+	// Paint sprites and check for collisions, but only if at least one sprite is active
+	// on this line.
+	if(line_buffer.active_sprite_slot) {
+		const int shift_advance = sprites_magnified_ ? 1 : 2;
+		// If this is the start of the line clip any part of any sprites that is off to the left.
+		if(!start) {
+			for(int index = 0; index < line_buffer.active_sprite_slot; ++index) {
+				LineBuffer::ActiveSprite &sprite = line_buffer.active_sprites[index];
+				if(sprite.x < 0) sprite.shift_position -= shift_advance * sprite.x;
+			}
+		}
+
+		int sprite_buffer[256];
+		int sprite_collision = 0;
+		memset(&sprite_buffer[start], 0, size_t(end - start)*sizeof(sprite_buffer[0]));
+
+		constexpr uint32_t sprite_colour_selection_masks[2] = {0x00000000, 0xffffffff};
+		constexpr int colour_masks[16] = {0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+
+		// Draw all sprites into the sprite buffer.
+		const int shifter_target = sprites_16x16_ ? 32 : 16;
+		for(int index = line_buffer.active_sprite_slot - 1; index >= 0; --index) {
+			LineBuffer::ActiveSprite &sprite = line_buffer.active_sprites[index];
+			if(sprite.shift_position < shifter_target) {
+				const int pixel_start = std::max(start, sprite.x);
+				for(int c = pixel_start; c < end && sprite.shift_position < shifter_target; ++c) {
+					const int shift = (sprite.shift_position >> 1) ^ 7;
+					int sprite_colour = (sprite.image[shift >> 3] >> (shift & 7)) & 1;
+
+					// A colision is detected regardless of sprite colour ...
+					sprite_collision |= sprite_buffer[c] & sprite_colour;
+					sprite_buffer[c] |= sprite_colour;
+
+					// ... but a sprite with the transparent colour won't actually be visible.
+					sprite_colour &= colour_masks[sprite.image[2]&15];
+					pixel_origin_[c] =
+						(pixel_origin_[c] & sprite_colour_selection_masks[sprite_colour^1]) |
+						(palette[sprite.image[2]&15] & sprite_colour_selection_masks[sprite_colour]);
+
+					sprite.shift_position += shift_advance;
+				}
+			}
+		}
+
+		status_ |= sprite_collision << StatusSpriteCollisionShift;
+	}
+}
+
+template <Personality personality>
+void Base<personality>::draw_tms_text(int start, int end) {
+	LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
+	const uint32_t colours[2] = { palette[background_colour_], palette[text_colour_] };
+
+	const int shift = start % 6;
+	int byte_column = start / 6;
+	int pattern = Numeric::bit_reverse(line_buffer.patterns[byte_column][0]) >> shift;
+	int pixels_left = end - start;
+	int length = std::min(pixels_left, 6 - shift);
+	while(true) {
+		pixels_left -= length;
+		for(int c = 0; c < length; ++c) {
+			pixel_target_[c] = colours[pattern&0x01];
+			pattern >>= 1;
+		}
+		pixel_target_ += length;
+
+		if(!pixels_left) break;
+		length = std::min(6, pixels_left);
+		byte_column++;
+		pattern = Numeric::bit_reverse(line_buffer.patterns[byte_column][0]);
+	}
+}
+
+// MARK: - Master System
+
+template <Personality personality>
+void Base<personality>::draw_sms(int start, int end, uint32_t cram_dot) {
+	LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
+	int colour_buffer[256];
+
+	/*
+		Add extra border for any pixels that fall before the fine scroll.
+	*/
+	int tile_start = start, tile_end = end;
+	int tile_offset = start;
+	if(read_pointer_.row >= 16 || !master_system_.horizontal_scroll_lock) {
+		for(int c = start; c < (line_buffer.latched_horizontal_scroll & 7); ++c) {
+			colour_buffer[c] = 16 + background_colour_;
+			++tile_offset;
+		}
+
+		// Remove the border area from that to which tiles will be drawn.
+		tile_start = std::max(start - (line_buffer.latched_horizontal_scroll & 7), 0);
+		tile_end = std::max(end - (line_buffer.latched_horizontal_scroll & 7), 0);
+	}
+
+
+	uint32_t pattern;
+	uint8_t *const pattern_index = reinterpret_cast<uint8_t *>(&pattern);
+
+	/*
+		Add background tiles; these will fill the colour_buffer with values in which
+		the low five bits are a palette index, and bit six is set if this tile has
+		priority over sprites.
+	*/
+	if(tile_start < end) {
+		const int shift = tile_start & 7;
+		int byte_column = tile_start >> 3;
+		int pixels_left = tile_end - tile_start;
+		int length = std::min(pixels_left, 8 - shift);
+
+		pattern = *reinterpret_cast<const uint32_t *>(line_buffer.patterns[byte_column]);
+		if(line_buffer.names[byte_column].flags&2)
+			pattern >>= shift;
+		else
+			pattern <<= shift;
+
+		while(true) {
+			const int palette_offset = (line_buffer.names[byte_column].flags&0x18) << 1;
+			if(line_buffer.names[byte_column].flags&2) {
+				for(int c = 0; c < length; ++c) {
+					colour_buffer[tile_offset] =
+						((pattern_index[3] & 0x01) << 3) |
+						((pattern_index[2] & 0x01) << 2) |
+						((pattern_index[1] & 0x01) << 1) |
+						((pattern_index[0] & 0x01) << 0) |
+						palette_offset;
+					++tile_offset;
+					pattern >>= 1;
+				}
+			} else {
+				for(int c = 0; c < length; ++c) {
+					colour_buffer[tile_offset] =
+						((pattern_index[3] & 0x80) >> 4) |
+						((pattern_index[2] & 0x80) >> 5) |
+						((pattern_index[1] & 0x80) >> 6) |
+						((pattern_index[0] & 0x80) >> 7) |
+						palette_offset;
+					++tile_offset;
+					pattern <<= 1;
+				}
+			}
+
+			pixels_left -= length;
+			if(!pixels_left) break;
+
+			length = std::min(8, pixels_left);
+			byte_column++;
+			pattern = *reinterpret_cast<const uint32_t *>(line_buffer.patterns[byte_column]);
+		}
+	}
+
+	/*
+		Apply sprites (if any).
+	*/
+	if(line_buffer.active_sprite_slot) {
+		const int shift_advance = sprites_magnified_ ? 1 : 2;
+
+		// If this is the start of the line clip any part of any sprites that is off to the left.
+		if(!start) {
+			for(int index = 0; index < line_buffer.active_sprite_slot; ++index) {
+				LineBuffer::ActiveSprite &sprite = line_buffer.active_sprites[index];
+				if(sprite.x < 0) sprite.shift_position -= shift_advance * sprite.x;
+			}
+		}
+
+		int sprite_buffer[256];
+		int sprite_collision = 0;
+		memset(&sprite_buffer[start], 0, size_t(end - start)*sizeof(sprite_buffer[0]));
+
+		// Draw all sprites into the sprite buffer.
+		for(int index = line_buffer.active_sprite_slot - 1; index >= 0; --index) {
+			LineBuffer::ActiveSprite &sprite = line_buffer.active_sprites[index];
+			if(sprite.shift_position < 16) {
+				const int pixel_start = std::max(start, sprite.x);
+
+				// TODO: it feels like the work below should be simplifiable;
+				// the double shift in particular, and hopefully the variable shift.
+				for(int c = pixel_start; c < end && sprite.shift_position < 16; ++c) {
+					const int shift = (sprite.shift_position >> 1);
+					const int sprite_colour =
+						(((sprite.image[3] << shift) & 0x80) >> 4) |
+						(((sprite.image[2] << shift) & 0x80) >> 5) |
+						(((sprite.image[1] << shift) & 0x80) >> 6) |
+						(((sprite.image[0] << shift) & 0x80) >> 7);
+
+					if(sprite_colour) {
+						sprite_collision |= sprite_buffer[c];
+						sprite_buffer[c] = sprite_colour | 0x10;
+					}
+
+					sprite.shift_position += shift_advance;
+				}
+			}
+		}
+
+		// Draw the sprite buffer onto the colour buffer, wherever the tile map doesn't have
+		// priority (or is transparent).
+		for(int c = start; c < end; ++c) {
+			if(
+				sprite_buffer[c] &&
+				(!(colour_buffer[c]&0x20) || !(colour_buffer[c]&0xf))
+			) colour_buffer[c] = sprite_buffer[c];
+		}
+
+		if(sprite_collision)
+			status_ |= StatusSpriteCollision;
+	}
+
+	// Map from the 32-colour buffer to real output pixels, applying the specific CRAM dot if any.
+	pixel_target_[start] = master_system_.colour_ram[colour_buffer[start] & 0x1f] | cram_dot;
+	for(int c = start+1; c < end; ++c) {
+		pixel_target_[c] = master_system_.colour_ram[colour_buffer[c] & 0x1f];
+	}
+
+	// If the VDP is set to hide the left column and this is the final call that'll come
+	// this line, hide it.
+	if(end == 256) {
+		if(master_system_.hide_left_column) {
+			pixel_origin_[0] = pixel_origin_[1] = pixel_origin_[2] = pixel_origin_[3] =
+			pixel_origin_[4] = pixel_origin_[5] = pixel_origin_[6] = pixel_origin_[7] =
+				master_system_.colour_ram[16 + background_colour_];
+		}
+	}
+}
+
+// MARK: - Yamaha
+
+// TODO.
+
+// MARK: - Mega Drive
+
+// TODO.
+
+#endif /* Draw_hpp */
--- a/Components/9918/Implementation/Fetch.hpp
+++ b/Components/9918/Implementation/Fetch.hpp
@ -0,0 +1,497 @@
+//
+//  Fetch.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 01/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef Fetch_hpp
+#define Fetch_hpp
+
+/*
+	Fetching routines follow below; they obey the following rules:
+
+		1)	input is a start position and an end position; they should perform the proper
+			operations for the period: start <= time < end.
+		2)	times are measured relative to a 172-cycles-per-line clock (so: they directly
+			count access windows on the TMS and Master System).
+		3)	time 0 is the beginning of the access window immediately after the last pattern/data
+			block fetch that would contribute to this line, in a normal 32-column mode. So:
+
+				* it's cycle 309 on Mattias' TMS diagram;
+				* it's cycle 1238 on his V9938 diagram;
+				* it's after the last background render block in Mask of Destiny's Master System timing diagram.
+
+			That division point was selected, albeit arbitrarily, because it puts all the tile
+			fetches for a single line into the same [0, 171] period.
+
+		4)	all of these functions are templated with a `use_end` parameter. That will be true if
+			end is < 172, false otherwise. So functions can use it to eliminate should-exit-not checks,
+			for the more usual path of execution.
+
+	Provided for the benefit of the methods below:
+
+		*	the function external_slot(), which will perform any pending VRAM read/write.
+		*	the macros slot(n) and external_slot(n) which can be used to schedule those things inside a
+			switch(start)-based implementation.
+
+	All functions should just spool data to intermediary storage. This is because for most VDPs there is
+	a decoupling between fetch pattern and output pattern, and it's neater to keep the same division
+	for the exceptions.
+*/
+
+#define slot(n)	\
+	if(use_end && end == n) return;	\
+	[[fallthrough]];				\
+	case n
+
+#define external_slot(n)	\
+	slot(n): do_external_slot(to_internal<personality, Clock::TMSMemoryWindow>(n));
+
+#define external_slots_2(n)	\
+	external_slot(n);		\
+	external_slot(n+1);
+
+#define external_slots_4(n)	\
+	external_slots_2(n);	\
+	external_slots_2(n+2);
+
+#define external_slots_8(n)	\
+	external_slots_4(n);	\
+	external_slots_4(n+4);
+
+#define external_slots_16(n)	\
+	external_slots_8(n);		\
+	external_slots_8(n+8);
+
+#define external_slots_32(n)	\
+	external_slots_16(n);		\
+	external_slots_16(n+16);
+
+
+// MARK: - TMS9918
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_tms_refresh(int start, int end) {
+#define refresh(location)		\
+	slot(location):				\
+	external_slot(location+1);
+
+#define refreshes_2(location)	\
+	refresh(location);			\
+	refresh(location+2);
+
+#define refreshes_4(location)	\
+	refreshes_2(location);		\
+	refreshes_2(location+4);
+
+#define refreshes_8(location)	\
+	refreshes_4(location);		\
+	refreshes_4(location+8);
+
+	switch(start) {
+		default: assert(false);
+
+		/* 44 external slots */
+		external_slots_32(0)
+		external_slots_8(32)
+		external_slots_4(40)
+
+		/* 64 refresh/external slot pairs (= 128 windows) */
+		refreshes_8(44);
+		refreshes_8(60);
+		refreshes_8(76);
+		refreshes_8(92);
+		refreshes_8(108);
+		refreshes_8(124);
+		refreshes_8(140);
+		refreshes_8(156);
+
+		return;
+	}
+
+#undef refreshes_8
+#undef refreshes_4
+#undef refreshes_2
+#undef refresh
+}
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_tms_text(int start, int end) {
+#define fetch_tile_name(location, column)		slot(location): line_buffer.names[column].offset = ram_[row_base + column];
+#define fetch_tile_pattern(location, column)	slot(location): line_buffer.patterns[column][0] = ram_[row_offset + size_t(line_buffer.names[column].offset << 3)];
+
+#define fetch_column(location, column)	\
+	fetch_tile_name(location, column);	\
+	external_slot(location+1);	\
+	fetch_tile_pattern(location+2, column);
+
+#define fetch_columns_2(location, column)	\
+	fetch_column(location, column);	\
+	fetch_column(location+3, column+1);
+
+#define fetch_columns_4(location, column)	\
+	fetch_columns_2(location, column);	\
+	fetch_columns_2(location+6, column+2);
+
+#define fetch_columns_8(location, column)	\
+	fetch_columns_4(location, column);	\
+	fetch_columns_4(location+12, column+4);
+
+	LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+	const size_t row_base = pattern_name_address_ & (0x3c00 | size_t(write_pointer_.row >> 3) * 40);
+	const size_t row_offset = pattern_generator_table_address_ & (0x3800 | (write_pointer_.row & 7));
+
+	switch(start) {
+		default: assert(false);
+
+			/* 47 external slots (= 47 windows) */
+			external_slots_32(0)
+			external_slots_8(32)
+			external_slots_4(40)
+			external_slots_2(44)
+			external_slot(46)
+
+			/* 40 column fetches (= 120 windows) */
+			fetch_columns_8(47, 0);
+			fetch_columns_8(71, 8);
+			fetch_columns_8(95, 16);
+			fetch_columns_8(119, 24);
+			fetch_columns_8(143, 32);
+
+			/* 5 more external slots */
+			external_slots_4(167);
+			external_slot(171);
+
+		return;
+	}
+
+#undef fetch_columns_8
+#undef fetch_columns_4
+#undef fetch_columns_2
+#undef fetch_column
+#undef fetch_tile_pattern
+#undef fetch_tile_name
+}
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_tms_character(int start, int end) {
+#define sprite_fetch_coordinates(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+		line_buffer.active_sprites[sprite].x = \
+			ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f81 | (line_buffer.active_sprites[sprite].index << 2))\
+			];
+
+	// This implementation doesn't refetch Y; it's unclear to me
+	// whether it's refetched.
+
+#define sprite_fetch_graphics(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+	slot(location+2):	\
+	slot(location+3):	{\
+		const uint8_t name = ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f82 | (line_buffer.active_sprites[sprite].index << 2))\
+			] & (sprites_16x16_ ? ~3 : ~0);\
+		line_buffer.active_sprites[sprite].image[2] = ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f83 | (line_buffer.active_sprites[sprite].index << 2))\
+			];\
+		line_buffer.active_sprites[sprite].x -= (line_buffer.active_sprites[sprite].image[2] & 0x80) >> 2;\
+		const size_t graphic_location = sprite_generator_table_address_ & size_t(0x3800 | (name << 3) | line_buffer.active_sprites[sprite].row);	\
+		line_buffer.active_sprites[sprite].image[0] = ram_[graphic_location];\
+		line_buffer.active_sprites[sprite].image[1] = ram_[graphic_location+16];\
+	}
+
+#define sprite_fetch_block(location, sprite)	\
+	sprite_fetch_coordinates(location, sprite)	\
+	sprite_fetch_graphics(location+2, sprite)
+
+#define sprite_y_read(location, sprite)	\
+	slot(location): posit_sprite(sprite_selection_buffer, sprite, ram_[sprite_attribute_table_address_ & (((sprite) << 2) | 0x3f80)], write_pointer_.row);
+
+#define fetch_tile_name(column) line_buffer.names[column].offset = ram_[(row_base + column) & 0x3fff];
+
+#define fetch_tile(column)	{\
+		line_buffer.patterns[column][1] = ram_[(colour_base + size_t((line_buffer.names[column].offset << 3) >> colour_name_shift)) & 0x3fff];		\
+		line_buffer.patterns[column][0] = ram_[(pattern_base + size_t(line_buffer.names[column].offset << 3)) & 0x3fff];	\
+	}
+
+#define background_fetch_block(location, column, sprite)	\
+	slot(location):	fetch_tile_name(column)		\
+	external_slot(location+1);	\
+	slot(location+2):	\
+	slot(location+3): fetch_tile(column)	\
+	slot(location+4): fetch_tile_name(column+1)	\
+	sprite_y_read(location+5, sprite);	\
+	slot(location+6):	\
+	slot(location+7): fetch_tile(column+1)	\
+	slot(location+8): fetch_tile_name(column+2)	\
+	sprite_y_read(location+9, sprite+1);	\
+	slot(location+10):	\
+	slot(location+11): fetch_tile(column+2)	\
+	slot(location+12): fetch_tile_name(column+3)	\
+	sprite_y_read(location+13, sprite+2);	\
+	slot(location+14):	\
+	slot(location+15): fetch_tile(column+3)
+
+	LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+	LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
+	const size_t row_base = pattern_name_address_ & (size_t((write_pointer_.row << 2)&~31) | 0x3c00);
+
+	size_t pattern_base = pattern_generator_table_address_;
+	size_t colour_base = colour_table_address_;
+	int colour_name_shift = 6;
+
+	if(screen_mode_ == ScreenMode::Graphics) {
+		// If this is high resolution mode, allow the row number to affect the pattern and colour addresses.
+		pattern_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
+		colour_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
+
+		colour_base += size_t(write_pointer_.row & 7);
+		colour_name_shift = 0;
+	} else {
+		colour_base &= size_t(0xffc0);
+		pattern_base &= size_t(0x3800);
+	}
+
+	if(screen_mode_ == ScreenMode::MultiColour) {
+		pattern_base += size_t((write_pointer_.row >> 2) & 7);
+	} else {
+		pattern_base += size_t(write_pointer_.row & 7);
+	}
+
+	switch(start) {
+		default: assert(false);
+
+		external_slots_2(0);
+
+		sprite_fetch_block(2, 0);
+		sprite_fetch_block(8, 1);
+		sprite_fetch_coordinates(14, 2);
+
+		external_slots_4(16);
+		external_slot(20);
+
+		sprite_fetch_graphics(21, 2);
+		sprite_fetch_block(25, 3);
+
+		slot(31):
+			sprite_selection_buffer.reset_sprite_collection();
+			do_external_slot(to_internal<personality, Clock::TMSMemoryWindow>(31));
+		external_slots_2(32);
+		external_slot(34);
+
+		sprite_y_read(35, 0);
+		sprite_y_read(36, 1);
+		sprite_y_read(37, 2);
+		sprite_y_read(38, 3);
+		sprite_y_read(39, 4);
+		sprite_y_read(40, 5);
+		sprite_y_read(41, 6);
+		sprite_y_read(42, 7);
+
+		background_fetch_block(43, 0, 8);
+		background_fetch_block(59, 4, 11);
+		background_fetch_block(75, 8, 14);
+		background_fetch_block(91, 12, 17);
+		background_fetch_block(107, 16, 20);
+		background_fetch_block(123, 20, 23);
+		background_fetch_block(139, 24, 26);
+		background_fetch_block(155, 28, 29);
+
+		return;
+	}
+
+#undef background_fetch_block
+#undef fetch_tile
+#undef fetch_tile_name
+#undef sprite_y_read
+#undef sprite_fetch_block
+#undef sprite_fetch_graphics
+#undef sprite_fetch_coordinates
+}
+
+
+// MARK: - Master System
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_sms(int start, int end) {
+#define sprite_fetch(sprite)	{\
+		line_buffer.active_sprites[sprite].x = \
+			ram_[\
+				master_system_.sprite_attribute_table_address & size_t(0x3f80 | (line_buffer.active_sprites[sprite].index << 1))\
+			] - (master_system_.shift_sprites_8px_left ? 8 : 0);	\
+		const uint8_t name = ram_[\
+				master_system_.sprite_attribute_table_address & size_t(0x3f81 | (line_buffer.active_sprites[sprite].index << 1))\
+			] & (sprites_16x16_ ? ~1 : ~0);\
+		const size_t graphic_location = master_system_.sprite_generator_table_address & size_t(0x2000 | (name << 5) | (line_buffer.active_sprites[sprite].row << 2));	\
+		line_buffer.active_sprites[sprite].image[0] = ram_[graphic_location];	\
+		line_buffer.active_sprites[sprite].image[1] = ram_[graphic_location+1];	\
+		line_buffer.active_sprites[sprite].image[2] = ram_[graphic_location+2];	\
+		line_buffer.active_sprites[sprite].image[3] = ram_[graphic_location+3];	\
+	}
+
+#define sprite_fetch_block(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+	slot(location+2):	\
+	slot(location+3):	\
+	slot(location+4):	\
+	slot(location+5):	\
+		sprite_fetch(sprite);\
+		sprite_fetch(sprite+1);
+
+#define sprite_y_read(location, sprite)	\
+	slot(location):	\
+		posit_sprite(sprite_selection_buffer, sprite, ram_[master_system_.sprite_attribute_table_address & ((sprite) | 0x3f00)], write_pointer_.row);	\
+		posit_sprite(sprite_selection_buffer, sprite+1, ram_[master_system_.sprite_attribute_table_address & ((sprite + 1) | 0x3f00)], write_pointer_.row);	\
+
+#define fetch_tile_name(column, row_info)	{\
+		const size_t scrolled_column = (column - horizontal_offset) & 0x1f;\
+		const size_t address = row_info.pattern_address_base + (scrolled_column << 1);	\
+		line_buffer.names[column].flags = ram_[address+1];	\
+		line_buffer.names[column].offset = size_t(	\
+			(((line_buffer.names[column].flags&1) << 8) | ram_[address]) << 5	\
+		) + row_info.sub_row[(line_buffer.names[column].flags&4) >> 2];	\
+	}
+
+#define fetch_tile(column)	\
+	line_buffer.patterns[column][0] = ram_[line_buffer.names[column].offset];	\
+	line_buffer.patterns[column][1] = ram_[line_buffer.names[column].offset+1];	\
+	line_buffer.patterns[column][2] = ram_[line_buffer.names[column].offset+2];	\
+	line_buffer.patterns[column][3] = ram_[line_buffer.names[column].offset+3];
+
+#define background_fetch_block(location, column, sprite, row_info)	\
+	slot(location):	fetch_tile_name(column, row_info)		\
+	external_slot(location+1);					\
+	slot(location+2):	\
+	slot(location+3):	\
+	slot(location+4):	\
+		fetch_tile(column)					\
+		fetch_tile_name(column+1, row_info)	\
+		sprite_y_read(location+5, sprite);	\
+	slot(location+6):	\
+	slot(location+7):	\
+	slot(location+8):	\
+		fetch_tile(column+1)					\
+		fetch_tile_name(column+2, row_info)		\
+		sprite_y_read(location+9, sprite+2);	\
+	slot(location+10):	\
+	slot(location+11):	\
+	slot(location+12):	\
+		fetch_tile(column+2)					\
+		fetch_tile_name(column+3, row_info)		\
+		sprite_y_read(location+13, sprite+4);	\
+	slot(location+14):	\
+	slot(location+15): fetch_tile(column+3)
+
+	// Determine the coarse horizontal scrolling offset; this isn't applied on the first two lines if the programmer has requested it.
+	LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+	LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
+	const int horizontal_offset = (write_pointer_.row >= 16 || !master_system_.horizontal_scroll_lock) ? (line_buffer.latched_horizontal_scroll >> 3) : 0;
+
+	// Limit address bits in use if this is a SMS2 mode.
+	const bool is_tall_mode = mode_timing_.pixel_lines != 192;
+	const size_t pattern_name_address = master_system_.pattern_name_address | (is_tall_mode ? 0x800 : 0);
+	const size_t pattern_name_offset = is_tall_mode ? 0x100 : 0;
+
+	// Determine row info for the screen both (i) if vertical scrolling is applied; and (ii) if it isn't.
+	// The programmer can opt out of applying vertical scrolling to the right-hand portion of the display.
+	const int scrolled_row = (write_pointer_.row + master_system_.latched_vertical_scroll) % (is_tall_mode ? 256 : 224);
+	struct RowInfo {
+		size_t pattern_address_base;
+		size_t sub_row[2];
+	};
+	const RowInfo scrolled_row_info = {
+		(pattern_name_address & size_t(((scrolled_row & ~7) << 3) | 0x3800)) - pattern_name_offset,
+		{size_t((scrolled_row & 7) << 2), 28 ^ size_t((scrolled_row & 7) << 2)}
+	};
+	RowInfo row_info;
+	if(master_system_.vertical_scroll_lock) {
+		row_info.pattern_address_base = (pattern_name_address & size_t(((write_pointer_.row & ~7) << 3) | 0x3800)) - pattern_name_offset;
+		row_info.sub_row[0] = size_t((write_pointer_.row & 7) << 2);
+		row_info.sub_row[1] = 28 ^ size_t((write_pointer_.row & 7) << 2);
+	} else row_info = scrolled_row_info;
+
+	// ... and do the actual fetching, which follows this routine:
+	switch(start) {
+		default: assert(false);
+
+		sprite_fetch_block(0, 0);
+		sprite_fetch_block(6, 2);
+
+		external_slots_4(12);
+		external_slot(16);
+
+		sprite_fetch_block(17, 4);
+		sprite_fetch_block(23, 6);
+
+		slot(29):
+			sprite_selection_buffer.reset_sprite_collection();
+			do_external_slot(to_internal<personality, Clock::TMSMemoryWindow>(29));
+		external_slot(30);
+
+		sprite_y_read(31, 0);
+		sprite_y_read(32, 2);
+		sprite_y_read(33, 4);
+		sprite_y_read(34, 6);
+		sprite_y_read(35, 8);
+		sprite_y_read(36, 10);
+		sprite_y_read(37, 12);
+		sprite_y_read(38, 14);
+
+		background_fetch_block(39, 0, 16, scrolled_row_info);
+		background_fetch_block(55, 4, 22, scrolled_row_info);
+		background_fetch_block(71, 8, 28, scrolled_row_info);
+		background_fetch_block(87, 12, 34, scrolled_row_info);
+		background_fetch_block(103, 16, 40, scrolled_row_info);
+		background_fetch_block(119, 20, 46, scrolled_row_info);
+		background_fetch_block(135, 24, 52, row_info);
+		background_fetch_block(151, 28, 58, row_info);
+
+		external_slots_4(167);
+
+		return;
+	}
+
+#undef background_fetch_block
+#undef fetch_tile
+#undef fetch_tile_name
+#undef sprite_y_read
+#undef sprite_fetch_block
+#undef sprite_fetch
+}
+
+// MARK: - Yamaha
+
+// TODO.
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_yamaha_refresh(int start, int end) {
+	(void)start;
+	(void)end;
+}
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_yamaha_no_sprites(int start, int end) {
+	(void)start;
+	(void)end;
+}
+
+template <Personality personality>
+template<bool use_end> void Base<personality>::fetch_yamaha_sprites(int start, int end) {
+	(void)start;
+	(void)end;
+}
+
+// MARK: - Mega Drive
+
+// TODO.
+
+#undef external_slot
+#undef slot
+
+#endif /* Fetch_hpp */
--- a/Components/9918/Implementation/PersonalityTraits.hpp
+++ b/Components/9918/Implementation/PersonalityTraits.hpp
@ -0,0 +1,49 @@
+//
+//  PersonalityTraits.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 06/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef PersonalityTraits_hpp
+#define PersonalityTraits_hpp
+
+namespace TI {
+namespace TMS {
+
+// Genus determinants for the various personalityes.
+constexpr bool is_sega_vdp(Personality p) {
+	return p >= Personality::SMSVDP;
+}
+
+constexpr bool is_yamaha_vdp(Personality p) {
+	return p == Personality::V9938 || p == Personality::V9958;
+}
+
+// i.e. one with the original internal timings.
+constexpr bool is_classic_vdp(Personality p) {
+	return
+		p == Personality::TMS9918A ||
+		p == Personality::SMSVDP ||
+		p == Personality::SMS2VDP ||
+		p == Personality::GGVDP;
+}
+
+constexpr size_t memory_size(Personality p) {
+	switch(p) {
+		case TI::TMS::TMS9918A:
+		case TI::TMS::SMSVDP:
+		case TI::TMS::SMS2VDP:
+		case TI::TMS::GGVDP:	return 16 * 1024;
+		case TI::TMS::MDVDP:	return 64 * 1024;
+		case TI::TMS::V9938:	return 128 * 1024;
+		case TI::TMS::V9958:	return 192 * 1024;
+	}
+}
+
+}
+}
+
+
+#endif /* PersonalityTraits_hpp */
--- a/Machines/ColecoVision/ColecoVision.cpp
+++ b/Machines/ColecoVision/ColecoVision.cpp
@ -117,7 +117,6 @@ class ConcreteMachine:
 	public:
 		ConcreteMachine(const Analyser::Static::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
 			z80_(*this),
-			vdp_(TI::TMS::TMS9918A),
 			sn76489_(TI::SN76489::Personality::SN76489, audio_queue_, sn76489_divider),
 			ay_(GI::AY38910::Personality::AY38910, audio_queue_),
 			mixer_(sn76489_, ay_),
@ -379,7 +378,7 @@ class ConcreteMachine:
 		}

 		CPU::Z80::Processor<ConcreteMachine, false, false> z80_;
-		JustInTimeActor<TI::TMS::TMS9918> vdp_;
+		JustInTimeActor<TI::TMS::TMS9918<TI::TMS::Personality::TMS9918A>> vdp_;

 		Concurrency::AsyncTaskQueue<false> audio_queue_;
 		TI::SN76489 sn76489_;
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@ -146,7 +146,6 @@ class ConcreteMachine:

 		ConcreteMachine(const Target &target, const ROMMachine::ROMFetcher &rom_fetcher):
 			z80_(*this),
-			vdp_(TI::TMS::TMS9918A),
 			i8255_(i8255_port_handler_),
 			ay_(GI::AY38910::Personality::AY38910, audio_queue_),
 			audio_toggle_(audio_queue_),
@ -744,7 +743,7 @@ class ConcreteMachine:
 		};

 		CPU::Z80::Processor<ConcreteMachine, false, false> z80_;
-		JustInTimeActor<TI::TMS::TMS9918> vdp_;
+		JustInTimeActor<TI::TMS::TMS9918<TI::TMS::Personality::TMS9918A>> vdp_;
 		Intel::i8255::i8255<i8255PortHandler> i8255_;

 		Concurrency::AsyncTaskQueue<false> audio_queue_;
--- a/Machines/MasterSystem/MasterSystem.cpp
+++ b/Machines/MasterSystem/MasterSystem.cpp
@ -29,6 +29,7 @@
 #include "../../Analyser/Static/Sega/Target.hpp"

 #include <algorithm>
+#include <cassert>
 #include <iostream>

 namespace {
@ -77,7 +78,7 @@ class Joystick: public Inputs::ConcreteJoystick {
 		uint8_t state_ = 0xff;
 };

-class ConcreteMachine:
+template <Analyser::Static::Sega::Target::Model model> class ConcreteMachine:
 	public Machine,
 	public CPU::Z80::BusHandler,
 	public MachineTypes::TimedMachine,
@ -90,11 +91,9 @@ class ConcreteMachine:

 	public:
 		ConcreteMachine(const Analyser::Static::Sega::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
-			model_(target.model),
 			region_(target.region),
 			paging_scheme_(target.paging_scheme),
 			z80_(*this),
-			vdp_(tms_personality_for_model(target.model)),
 			sn76489_(
 				(target.model == Target::Model::SG1000) ? TI::SN76489::Personality::SN76489 : TI::SN76489::Personality::SMS,
 				audio_queue_,
@ -159,7 +158,7 @@ class ConcreteMachine:
 			page_cartridge();

 			// Map RAM.
-			if(is_master_system(model_)) {
+			if constexpr (is_master_system(model)) {
 				map(read_pointers_, ram_, 8*1024, 0xc000, 0x10000);
 				map(write_pointers_, ram_, 8*1024, 0xc000, 0x10000);
 			} else {
@ -311,7 +310,7 @@ class ConcreteMachine:
 					case CPU::Z80::PartialMachineCycle::Output:
 						switch(address & 0xc1) {
 							case 0x00:		// i.e. even ports less than 0x40.
-								if(is_master_system(model_)) {
+								if constexpr (is_master_system(model)) {
 									// TODO: Obey the RAM enable.
 									LOG("Memory control: " << PADHEX(2) << memory_control_);
 									memory_control_ = *cycle.value;
@ -431,7 +430,7 @@ class ConcreteMachine:
 		}

 	private:
-		static TI::TMS::Personality tms_personality_for_model(Analyser::Static::Sega::Target::Model model) {
+		static constexpr TI::TMS::Personality tms_personality() {
 			switch(model) {
 				default:
 				case Target::Model::SG1000:			return TI::TMS::TMS9918A;
@ -481,11 +480,10 @@ class ConcreteMachine:
 		}

 		using Target = Analyser::Static::Sega::Target;
-		const Target::Model model_;
 		const Target::Region region_;
 		const Target::PagingScheme paging_scheme_;
 		CPU::Z80::Processor<ConcreteMachine, false, false> z80_;
-		JustInTimeActor<TI::TMS::TMS9918> vdp_;
+		JustInTimeActor<TI::TMS::TMS9918<tms_personality()>> vdp_;

 		Concurrency::AsyncTaskQueue<false> audio_queue_;
 		TI::SN76489 sn76489_;
@ -559,7 +557,14 @@ using namespace Sega::MasterSystem;
 Machine *Machine::MasterSystem(const Analyser::Static::Target *target, const ROMMachine::ROMFetcher &rom_fetcher) {
 	using Target = Analyser::Static::Sega::Target;
 	const Target *const sega_target = dynamic_cast<const Target *>(target);
-	return new ConcreteMachine(*sega_target, rom_fetcher);
+
+	switch(sega_target->model) {
+		case Target::Model::SG1000:			return new ConcreteMachine<Target::Model::SG1000>(*sega_target, rom_fetcher);
+		case Target::Model::MasterSystem:	return new ConcreteMachine<Target::Model::MasterSystem>(*sega_target, rom_fetcher);
+		case Target::Model::MasterSystem2:	return new ConcreteMachine<Target::Model::MasterSystem2>(*sega_target, rom_fetcher);
+		default:
+			assert(false);
+	}
 }

 Machine::~Machine() {}
--- a/Numeric/BitReverse.hpp
+++ b/Numeric/BitReverse.hpp
@ -0,0 +1,62 @@
+//
+//  BitReverse.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 05/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef BitReverse_hpp
+#define BitReverse_hpp
+
+#include <cstdint>
+
+namespace Numeric {
+
+/// @returns @c source with the order of its bits reversed. E.g. if @c IntT is @c uint8_t then
+/// the reverse of bit pattern abcd efgh is hgfd dcba.
+template <typename IntT> constexpr IntT bit_reverse(IntT source);
+
+// The single-byte specialisation uses a lookup table.
+template<> constexpr uint8_t bit_reverse<uint8_t>(uint8_t source) {
+    struct ReverseTable {
+		static constexpr std::array<uint8_t, 256> reverse_table() {
+			std::array<uint8_t, 256> map{};
+			for(std::size_t c = 0; c < 256; ++c) {
+				map[c] = uint8_t(
+					((c & 0x80) >> 7) |
+					((c & 0x40) >> 5) |
+					((c & 0x20) >> 3) |
+					((c & 0x10) >> 1) |
+					((c & 0x08) << 1) |
+					((c & 0x04) << 3) |
+					((c & 0x02) << 5) |
+					((c & 0x01) << 7)
+				);
+			}
+			return map;
+		}
+    };
+
+	const std::array<uint8_t, 256> map = ReverseTable::reverse_table();
+	return map[source];
+}
+
+// All other versions just call the byte-level reverse the appropriate number of times.
+template <typename IntT> constexpr IntT bit_reverse(IntT source) {
+	IntT result;
+
+	uint8_t *src = reinterpret_cast<uint8_t *>(&source);
+	uint8_t *dest = reinterpret_cast<uint8_t *>(&result) + sizeof(result) - 1;
+	for(size_t c = 0; c < sizeof(source); c++) {
+		*dest = bit_reverse(*src);
+		++src;
+		--dest;
+	}
+
+	return result;
+}
+
+}
+
+#endif /* BitReverse_hpp */
--- a/Signal.xcodeproj/project.pbxproj
+++ b/Signal.xcodeproj/project.pbxproj
@ -137,8 +137,6 @@
 		4B0E04EA1FC9E5DA00F43484 /* CAS.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E04E81FC9E5DA00F43484 /* CAS.cpp */; };
 		4B0E04EB1FC9E78800F43484 /* CAS.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E04E81FC9E5DA00F43484 /* CAS.cpp */; };
 		4B0E04F11FC9EA9500F43484 /* MSX.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B79A4FF1FC913C900EEDAD5 /* MSX.cpp */; };
-		4B0E04FA1FC9FA3100F43484 /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E04F91FC9FA3100F43484 /* 9918.cpp */; };
-		4B0E04FB1FC9FA3100F43484 /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E04F91FC9FA3100F43484 /* 9918.cpp */; };
 		4B0E61071FF34737002A9DBD /* MSX.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E61051FF34737002A9DBD /* MSX.cpp */; };
 		4B0F1BB22602645900B85C66 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0F1BB02602645900B85C66 /* StaticAnalyser.cpp */; };
 		4B0F1BB32602645900B85C66 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0F1BB02602645900B85C66 /* StaticAnalyser.cpp */; };
@ -229,6 +227,9 @@
 		4B3F76B925A1635300178AEC /* PowerPCDecoderTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B3F76B825A1635300178AEC /* PowerPCDecoderTests.mm */; };
 		4B3FCC40201EC24200960631 /* MultiMachine.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B3FCC3F201EC24200960631 /* MultiMachine.cpp */; };
 		4B3FE75E1F3CF68B00448EE4 /* CPM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B3FE75C1F3CF68B00448EE4 /* CPM.cpp */; };
+		4B43983929620FC7006B0BFC /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B43983829620FB1006B0BFC /* 9918.cpp */; };
+		4B43983A29620FC8006B0BFC /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B43983829620FB1006B0BFC /* 9918.cpp */; };
+		4B43983B29620FC9006B0BFC /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B43983829620FB1006B0BFC /* 9918.cpp */; };
 		4B448E811F1C45A00009ABD6 /* TZX.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B448E7F1F1C45A00009ABD6 /* TZX.cpp */; };
 		4B448E841F1C4C480009ABD6 /* PulseQueuedTape.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B448E821F1C4C480009ABD6 /* PulseQueuedTape.cpp */; };
 		4B44EBF51DC987AF00A7820C /* AllSuiteA.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4B44EBF41DC987AE00A7820C /* AllSuiteA.bin */; };
@ -352,7 +353,6 @@
 		4B7752C228217F5C0073E2C5 /* Spectrum.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B5D5C9525F56FC7001B4623 /* Spectrum.cpp */; };
 		4B7752C328217F720073E2C5 /* Z80.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B8DD39526360DDF00B3C866 /* Z80.cpp */; };
 		4B778EF023A5D68C0000D260 /* 68000Storage.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BFF1D3822337B0300838EA1 /* 68000Storage.cpp */; };
-		4B778EF123A5D6B50000D260 /* 9918.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0E04F91FC9FA3100F43484 /* 9918.cpp */; };
 		4B778EF323A5DB230000D260 /* PCMSegment.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B4518731F75E91800926311 /* PCMSegment.cpp */; };
 		4B778EF423A5DB3A0000D260 /* C1540.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B8334941F5E25B60097E338 /* C1540.cpp */; };
 		4B778EF523A5DB440000D260 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B894517201967B4007DE474 /* StaticAnalyser.cpp */; };
@ -1179,7 +1179,6 @@
 		4B0E04E81FC9E5DA00F43484 /* CAS.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = CAS.cpp; sourceTree = "<group>"; };
 		4B0E04E91FC9E5DA00F43484 /* CAS.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = CAS.hpp; sourceTree = "<group>"; };
 		4B0E04F81FC9FA3000F43484 /* 9918.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 9918.hpp; sourceTree = "<group>"; };
-		4B0E04F91FC9FA3100F43484 /* 9918.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = 9918.cpp; sourceTree = "<group>"; };
 		4B0E61051FF34737002A9DBD /* MSX.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; name = MSX.cpp; path = Parsers/MSX.cpp; sourceTree = "<group>"; };
 		4B0E61061FF34737002A9DBD /* MSX.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; name = MSX.hpp; path = Parsers/MSX.hpp; sourceTree = "<group>"; };
 		4B0F1BB02602645900B85C66 /* StaticAnalyser.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = StaticAnalyser.cpp; sourceTree = "<group>"; };
@ -1247,6 +1246,7 @@
 		4B228CDA24DA41880077EF25 /* ScanTarget.metal */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.metal; path = ScanTarget.metal; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.metal; };
 		4B24095A1C45DF85004DA684 /* Stepper.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Stepper.hpp; sourceTree = "<group>"; };
 		4B2530F3244E6773007980BF /* fm.json */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.json; path = fm.json; sourceTree = "<group>"; };
+		4B262BFF29691F55002EC0F7 /* PersonalityTraits.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = PersonalityTraits.hpp; sourceTree = "<group>"; };
 		4B2A332C1DB86821002876E3 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = "Clock Signal/Base.lproj/OricOptions.xib"; sourceTree = SOURCE_ROOT; };
 		4B2A53901D117D36003C6002 /* CSAudioQueue.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = CSAudioQueue.h; sourceTree = "<group>"; };
 		4B2A53911D117D36003C6002 /* CSAudioQueue.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = CSAudioQueue.m; sourceTree = "<group>"; };
@ -1317,6 +1317,11 @@
 		4B3FCC3F201EC24200960631 /* MultiMachine.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = MultiMachine.cpp; sourceTree = "<group>"; };
 		4B3FE75C1F3CF68B00448EE4 /* CPM.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = CPM.cpp; path = Parsers/CPM.cpp; sourceTree = "<group>"; };
 		4B3FE75D1F3CF68B00448EE4 /* CPM.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = CPM.hpp; path = Parsers/CPM.hpp; sourceTree = "<group>"; };
+		4B43983829620FB1006B0BFC /* 9918.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = 9918.cpp; sourceTree = "<group>"; };
+		4B43983C29621024006B0BFC /* ClockConverter.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = ClockConverter.hpp; sourceTree = "<group>"; };
+		4B43983E29628538006B0BFC /* Fetch.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Fetch.hpp; sourceTree = "<group>"; };
+		4B43983F2967459B006B0BFC /* Draw.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Draw.hpp; sourceTree = "<group>"; };
+		4B43984129674943006B0BFC /* BitReverse.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = BitReverse.hpp; sourceTree = "<group>"; };
 		4B448E7F1F1C45A00009ABD6 /* TZX.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = TZX.cpp; sourceTree = "<group>"; };
 		4B448E801F1C45A00009ABD6 /* TZX.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = TZX.hpp; sourceTree = "<group>"; };
 		4B448E821F1C4C480009ABD6 /* PulseQueuedTape.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PulseQueuedTape.cpp; sourceTree = "<group>"; };
@ -2398,7 +2403,6 @@
 		4B0E04F71FC9F2C800F43484 /* 9918 */ = {
 			isa = PBXGroup;
 			children = (
-				4B0E04F91FC9FA3100F43484 /* 9918.cpp */,
 				4B0E04F81FC9FA3000F43484 /* 9918.hpp */,
 				4BD388431FE34E060042B588 /* Implementation */,
 			);
@ -3288,6 +3292,7 @@
 		4B7BA03C23D55E7900B98D9E /* Numeric */ = {
 			isa = PBXGroup;
 			children = (
+				4B43984129674943006B0BFC /* BitReverse.hpp */,
 				4BD155312716362A00410C6E /* BitSpread.hpp */,
 				4B7BA03E23D55E7900B98D9E /* CRC.hpp */,
 				4B7BA03F23D55E7900B98D9E /* LFSR.hpp */,
@ -4733,7 +4738,12 @@
 		4BD388431FE34E060042B588 /* Implementation */ = {
 			isa = PBXGroup;
 			children = (
+				4B43983829620FB1006B0BFC /* 9918.cpp */,
 				4BD388411FE34E010042B588 /* 9918Base.hpp */,
+				4B43983C29621024006B0BFC /* ClockConverter.hpp */,
+				4B43983F2967459B006B0BFC /* Draw.hpp */,
+				4B43983E29628538006B0BFC /* Fetch.hpp */,
+				4B262BFF29691F55002EC0F7 /* PersonalityTraits.hpp */,
 			);
 			path = Implementation;
 			sourceTree = "<group>";
@ -5519,7 +5529,6 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				4B0E04FB1FC9FA3100F43484 /* 9918.cpp in Sources */,
 				4B1B88C9202E469400B67DFF /* MultiJoystickMachine.cpp in Sources */,
 				4BCE1DF225D4C3FA00AE7A2B /* Bus.cpp in Sources */,
 				4BC080DA26A25ADA00D03FD8 /* Amiga.cpp in Sources */,
@ -5529,6 +5538,7 @@
 				4B1B5900246E19FD009C171E /* State.cpp in Sources */,
 				4BC57CDA2436A62900FBC404 /* State.cpp in Sources */,
 				4B055ACB1FAE9AFB0060FFFF /* SerialBus.cpp in Sources */,
+				4B43983B29620FC9006B0BFC /* 9918.cpp in Sources */,
 				4B8318B122D3E53A006DB630 /* DiskIICard.cpp in Sources */,
 				4B055A9B1FAE85DA0060FFFF /* AcornADF.cpp in Sources */,
 				4B0E04F11FC9EA9500F43484 /* MSX.cpp in Sources */,
@ -5821,6 +5831,7 @@
 				4BC080CA26A238CC00D03FD8 /* AmigaADF.cpp in Sources */,
 				4B1A1B1E27320FBC00119335 /* Disk.cpp in Sources */,
 				4B92E26A234AE35100CD6D1B /* MFP68901.cpp in Sources */,
+				4B43983929620FC7006B0BFC /* 9918.cpp in Sources */,
 				4B051C97266EF5F600CA44E8 /* CSAppleII.mm in Sources */,
 				4B0ACC2A23775819008902D0 /* Video.cpp in Sources */,
 				4B54C0BF1F8D8F450050900F /* Keyboard.cpp in Sources */,
@ -5927,7 +5938,6 @@
 				4B17B58B20A8A9D9007CCA8F /* StringSerialiser.cpp in Sources */,
 				4B2E2D9D1C3A070400138695 /* Electron.cpp in Sources */,
 				4B051CA826781D6500CA44E8 /* StaticAnalyser.cpp in Sources */,
-				4B0E04FA1FC9FA3100F43484 /* 9918.cpp in Sources */,
 				4B69FB3D1C4D908A00B5F0AA /* Tape.cpp in Sources */,
 				4B4518841F75E91A00926311 /* UnformattedTrack.cpp in Sources */,
 				4B65086022F4CF8D009C1100 /* Keyboard.cpp in Sources */,
@ -6123,6 +6133,7 @@
 				4BE34438238389E10058E78F /* AtariSTVideoTests.mm in Sources */,
 				4BEF6AAC1D35D1C400E73575 /* DPLLTests.swift in Sources */,
 				4BE76CF922641ED400ACD6FA /* QLTests.mm in Sources */,
+				4B43983A29620FC8006B0BFC /* 9918.cpp in Sources */,
 				4B778F0923A5EC150000D260 /* OricTAP.cpp in Sources */,
 				4B3BA0CF1D318B44005DD7A7 /* MOS6522Bridge.mm in Sources */,
 				4B778F6023A5F3460000D260 /* Disk.cpp in Sources */,
@ -6138,7 +6149,6 @@
 				4B0DA67D282DCDF300C12F17 /* Instruction.cpp in Sources */,
 				4BFCA12B1ECBE7C400AC40C1 /* ZexallTests.swift in Sources */,
 				4B778F2223A5EDDD0000D260 /* PulseQueuedTape.cpp in Sources */,
-				4B778EF123A5D6B50000D260 /* 9918.cpp in Sources */,
 				4B051CB3267D3FF800CA44E8 /* EnterpriseNickTests.mm in Sources */,
 				4B9D0C4D22C7DA1A00DE1AD3 /* 68000ControlFlowTests.mm in Sources */,
 				4BB2A9AF1E13367E001A5C23 /* CRCTests.mm in Sources */,
--- a/SignalTests/MasterSystemVDPTests.mm
+++ b/SignalTests/MasterSystemVDPTests.mm
@ -19,8 +19,10 @@
 	[super setUp];
 }

+using VDP = TI::TMS::TMS9918<TI::TMS::Personality::SMSVDP>;
+
 - (void)testLineInterrupt {
-	TI::TMS::TMS9918 vdp(TI::TMS::Personality::SMSVDP);
+	VDP vdp;

 	// Disable end-of-frame interrupts, enable line interrupts.
 	vdp.write(1, 0x00);
@ -63,7 +65,7 @@
 }

 - (void)testFirstLineInterrupt {
-	TI::TMS::TMS9918 vdp(TI::TMS::Personality::SMSVDP);
+	VDP vdp;

 	// Disable end-of-frame interrupts, enable line interrupts, set an interrupt to occur every line.
 	vdp.write(1, 0x00);
@ -96,7 +98,7 @@
 }

 - (void)testInterruptPrediction {
-	TI::TMS::TMS9918 vdp(TI::TMS::Personality::SMSVDP);
+	VDP vdp;

 	for(int c = 0; c < 256; ++c) {
 		for(int with_eof = (c < 192) ? 0 : 1; with_eof < 2; ++with_eof) {
@ -144,7 +146,7 @@
 }

 - (void)testTimeUntilLine {
-	TI::TMS::TMS9918 vdp(TI::TMS::Personality::SMSVDP);
+	VDP vdp;

 	auto time_until_line = vdp.get_time_until_line(-1).as_integral();
 	for(int c = 0; c < 262*228*5; ++c) {
--- a/OSBindings/Qt/clksignal.pro
+++ b/OSBindings/Qt/clksignal.pro
@ -65,6 +65,7 @@ SOURCES += \
 	$$SRC/Components/8272/*.cpp \
 	$$SRC/Components/8530/*.cpp \
 	$$SRC/Components/9918/*.cpp \
+	$$SRC/Components/9918/Implementation/*.cpp \
 	$$SRC/Components/AudioToggle/*.cpp \
 	$$SRC/Components/AY38910/*.cpp \
 	$$SRC/Components/DiskII/*.cpp \