Merge branch 'master' into NIBSlipBits

Analyser/Static/PCCompatible/Target.hpp

@@ -20,10 +20,17 @@ struct Target: public Analyser::Static::Target, public Reflection::StructImpl<Ta
 		CGA);
 	VideoAdaptor adaptor = VideoAdaptor::CGA;
 
+	ReflectableEnum(Speed,
+		ApproximatelyOriginal,
+		Fast);
+	Speed speed = Speed::Fast;
+
 	Target() : Analyser::Static::Target(Machine::PCCompatible) {
 		if(needs_declare()) {
-			DeclareField(adaptor);
 			AnnounceEnum(VideoAdaptor);
+			AnnounceEnum(Speed);
+			DeclareField(adaptor);
+			DeclareField(speed);
 		}
 	}
 };

Analyser/Static/StaticAnalyser.cpp

@@ -50,6 +50,7 @@
 #include "../../Storage/Disk/DiskImage/Formats/FAT12.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/HFE.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/IPF.hpp"
+#include "../../Storage/Disk/DiskImage/Formats/IMD.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/MacintoshIMG.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/MSA.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/NIB.hpp"
@@ -182,6 +183,7 @@ static Media GetMediaAndPlatforms(const std::string &file_name, TargetPlatform::
 			// HFE (TODO: switch to AllDisk once the MSX stops being so greedy)
 	Format("ima", result.disks, Disk::DiskImageHolder<Storage::Disk::FAT12>, TargetPlatform::PCCompatible)			// IMG (MS-DOS style)
 	Format("image", result.disks, Disk::DiskImageHolder<Storage::Disk::MacintoshIMG>, TargetPlatform::Macintosh)	// IMG (DiskCopy 4.2)
+	Format("imd", result.disks, Disk::DiskImageHolder<Storage::Disk::IMD>, TargetPlatform::PCCompatible)			// IMD
 	Format("img", result.disks, Disk::DiskImageHolder<Storage::Disk::MacintoshIMG>, TargetPlatform::Macintosh)		// IMG (DiskCopy 4.2)
 
 	// Treat PC booter as a potential backup only if this doesn't parse as a FAT12.

Components/8272/Status.hpp

@@ -47,12 +47,12 @@ enum class Status1: uint8_t {
 };
 
 enum class Status2: uint8_t {
-	DeletedControlMark	= 0x40,
+	DeletedControlMark		= 0x40,
-	DataCRCError 		= 0x20,
+	DataCRCError 			= 0x20,
-	WrongCyinder		= 0x10,
+	WrongCyinder			= 0x10,
-	ScanEqualHit		= 0x08,
+	ScanEqualHit			= 0x08,
-	ScanNotSatisfied	= 0x04,
+	ScanNotSatisfied		= 0x04,
-	BadCylinder			= 0x02,
+	BadCylinder				= 0x02,
 	MissingDataAddressMark	= 0x01,
 };
 

Machines/PCCompatible/CGA.hpp

@@ -15,41 +15,6 @@
 
 namespace PCCompatible {
 
-static constexpr uint8_t DarkCyan		= 0b00'10'10;
-static constexpr uint8_t DarkMagenta	= 0b10'00'10;
-static constexpr uint8_t DarkGrey		= 0b10'10'10;
-
-static constexpr uint8_t DarkGreen		= 0b00'10'00;
-static constexpr uint8_t DarkRed		= 0b10'00'00;
-static constexpr uint8_t DarkYellow		= 0b10'10'00;
-
-static constexpr uint8_t Brown			= 0b10'01'00;
-
-/// @returns @c Brown if @c source is @c DarkYellow; @c source otherwise.
-constexpr uint8_t yellow_to_brown(uint8_t source) {
-	return (source == DarkYellow) ? Brown : source;
-}
-
-/// @returns The brightened (i.e. high intensity) version of @c source.
-constexpr uint8_t bright(uint8_t source) {
-	return source | (source >> 1);
-}
-
-/// Maps the RGB TTL triplet @c source to an appropriate output colour.
-constexpr uint8_t rgb(uint8_t source) {
-	return uint8_t(
-		((source & 0x01) << 1) |
-		((source & 0x02) << 2) |
-		((source & 0x04) << 3)
-	);
-}
-
-/// Maps the RGBI value in @c source to an appropriate output colour, including potential yellow-to-brown conversion.
-constexpr uint8_t rgbi(uint8_t source) {
-	const uint8_t result = rgb(source);
-	return (source & 0x10) ? bright(result) : yellow_to_brown(result);
-}
-
 class CGA {
 	public:
 		CGA() : crtc_(Motorola::CRTC::Personality::HD6845S, outputter_) {}
@@ -102,7 +67,7 @@ class CGA {
 						// b1: 1 => positive edge from light pen has set trigger;
 						// b0: 1 => safe to write to VRAM now without causing snow.
 						(crtc_.get_bus_state().vsync ? 0b1001 : 0b0000) |
-						(crtc_.get_bus_state().hsync ? 0b0001 : 0b0000) |
+						(crtc_.get_bus_state().display_enable ? 0b0000 : 0b0001) |
 						0b0100;
 
 				default: return 0xff;
@@ -113,6 +78,7 @@ class CGA {
 
 		void set_display_type(Outputs::Display::DisplayType display_type) {
 			outputter_.crt.set_display_type(display_type);
+			outputter_.set_is_composite(Outputs::Display::is_composite(display_type));
 		}
 		Outputs::Display::DisplayType get_display_type() const {
 			return outputter_.crt.get_display_type();
@@ -165,6 +131,11 @@ class CGA {
 				update_palette();
 			}
 
+			void set_is_composite(bool is_composite) {
+				is_composite_ = is_composite;
+				update_palette();
+			}
+
 			void set_colours(uint8_t value) {
 				colours_ = value;
 				update_palette();
@@ -207,6 +178,7 @@ class CGA {
 				// Determine new output state.
 				update_hsync(state.hsync);
 				const OutputState new_state = implied_state(state);
+				static constexpr uint8_t colour_phase = 200;
 
 				// Upon either a state change or just having accumulated too much local time...
 				if(
@@ -219,7 +191,7 @@ class CGA {
 					// (1) flush preexisting state.
 					if(count) {
 						switch(output_state) {
-							case OutputState::Sync:			crt.output_sync(count * active_clock_divider);				break;
+							case OutputState::Sync:			crt.output_sync(count * active_clock_divider);							break;
 							case OutputState::Border:
 								if(active_border_colour) {
 									crt.output_blank(count * active_clock_divider);
@@ -227,8 +199,8 @@ class CGA {
 									crt.output_level<uint8_t>(count * active_clock_divider, active_border_colour);
 								}
 							break;
-							case OutputState::ColourBurst:	crt.output_colour_burst(count * active_clock_divider, 0);	break;
+							case OutputState::ColourBurst:	crt.output_colour_burst(count * active_clock_divider, colour_phase);	break;
-							case OutputState::Pixels:		flush_pixels();												break;
+							case OutputState::Pixels:		flush_pixels();															break;
 						}
 					}
 
@@ -335,18 +307,21 @@ class CGA {
 
 				// Apply blink or background intensity.
 				if(control_ & 0x20) {
+					// Set both colours to black if within a blink; otherwise consider a yellow-to-brown conversion.
 					if((attributes & 0x80) && (state.field_count & 16)) {
-						std::swap(colours[0], colours[1]);
+						colours[0] = colours[1] = 0;
+					} else {
+						colours[0] = yellow_to_brown(colours[0]);
 					}
 				} else {
 					if(attributes & 0x80) {
 						colours[0] = bright(colours[0]);
+					} else {
+						// Yellow to brown definitely doesn't apply if the colour has been brightened.
+						colours[0] = yellow_to_brown(colours[0]);
 					}
 				}
 
-				// Potentially remap dark yellow to brown.
-				colours[0] = yellow_to_brown(colours[0]);
-
 				// Draw according to ROM contents.
 				pixel_pointer[0] = (row & 0x80) ? colours[1] : colours[0];
 				pixel_pointer[1] = (row & 0x40) ? colours[1] : colours[0];
@@ -384,6 +359,7 @@ class CGA {
 			int pixels_per_tick = 8;
 			uint8_t colours_ = 0;
 			uint8_t control_ = 0;
+			bool is_composite_ = false;
 			enum class Mode {
 				Pixels640, Pixels320, Text,
 			} mode_ = Mode::Text;
@@ -425,10 +401,48 @@ class CGA {
 				border_colour = (mode_ != Mode::Pixels640) ? palette320[0] : 0;
 			}
 
+			//
+			// Named colours and mapping logic.
+			//
+			static constexpr uint8_t DarkCyan		= 0b00'10'10;
+			static constexpr uint8_t DarkMagenta	= 0b10'00'10;
+			static constexpr uint8_t DarkGrey		= 0b10'10'10;
+
+			static constexpr uint8_t DarkGreen		= 0b00'10'00;
+			static constexpr uint8_t DarkRed		= 0b10'00'00;
+			static constexpr uint8_t DarkYellow		= 0b10'10'00;
+
+			static constexpr uint8_t Brown			= 0b10'01'00;
+
+			/// @returns @c Brown if @c source is @c DarkYellow and composite output is not enabled; @c source otherwise.
+			constexpr uint8_t yellow_to_brown(uint8_t source) {
+				return (source == DarkYellow && !is_composite_) ? Brown : source;
+			}
+
+			/// @returns The brightened (i.e. high intensity) version of @c source.
+			constexpr uint8_t bright(uint8_t source) {
+				return source | (source >> 1);
+			}
+
+			/// Maps the RGB TTL triplet @c source to an appropriate output colour.
+			constexpr uint8_t rgb(uint8_t source) {
+				return uint8_t(
+					((source & 0x01) << 1) |
+					((source & 0x02) << 2) |
+					((source & 0x04) << 3)
+				);
+			}
+
+			/// Maps the RGBI value in @c source to an appropriate output colour, including potential yellow-to-brown conversion.
+			constexpr uint8_t rgbi(uint8_t source) {
+				const uint8_t result = rgb(source);
+				return (source & 0x10) ? bright(result) : yellow_to_brown(result);
+			}
 		} outputter_;
 		Motorola::CRTC::CRTC6845<CRTCOutputter, Motorola::CRTC::CursorType::MDA> crtc_;
 
 		int full_clock_ = 0;
+
 };
 
 }

Machines/PCCompatible/DMA.hpp

@@ -31,7 +31,7 @@ class i8237 {
 
 		template <int address>
 		void write(uint8_t value) {
-			printf("DMA: Write %02x to %d\n", value, address);
+//			printf("DMA: Write %02x to %d\n", value, address);
 
 			switch(address) {
 				default: {
@@ -66,7 +66,7 @@ class i8237 {
 
 		template <int address>
 		uint8_t read() {
-			printf("DMA: Read %d\n", address);
+//			printf("DMA: Read %d\n", address);
 			switch(address) {
 				default: {
 					constexpr int channel = (address >> 1) & 3;
@@ -146,7 +146,7 @@ class i8237 {
 				channel.transfer_complete = false;
 			}
 
-			printf("DMA: status is %02x\n", result);
+//			printf("DMA: status is %02x\n", result);
 
 			return result;
 		}
@@ -157,19 +157,19 @@ class i8237 {
 		}
 
 		void flip_flop_reset() {
-			printf("DMA: Flip flop reset\n");
+//			printf("DMA: Flip flop reset\n");
 			next_access_low_ = true;
 		}
 
 		void mask_reset() {
-			printf("DMA: Mask reset\n");
+//			printf("DMA: Mask reset\n");
 			for(auto &channel : channels_) {
 				channel.mask = false;
 			}
 		}
 
 		void master_reset() {
-			printf("DMA: Master reset\n");
+//			printf("DMA: Master reset\n");
 			flip_flop_reset();
 			for(auto &channel : channels_) {
 				channel.mask = true;
@@ -183,17 +183,17 @@ class i8237 {
 		}
 
 		void set_reset_mask(uint8_t value) {
-			printf("DMA: Set/reset mask %02x\n", value);
+//			printf("DMA: Set/reset mask %02x\n", value);
 			channels_[value & 3].mask = value & 4;
 		}
 
 		void set_reset_request(uint8_t value) {
-			printf("DMA: Set/reset request %02x\n", value);
+//			printf("DMA: Set/reset request %02x\n", value);
 			channels_[value & 3].request = value & 4;
 		}
 
 		void set_mask(uint8_t value) {
-			printf("DMA: Set mask %02x\n", value);
+//			printf("DMA: Set mask %02x\n", value);
 			channels_[0].mask = value & 1;
 			channels_[1].mask = value & 2;
 			channels_[2].mask = value & 4;
@@ -201,7 +201,7 @@ class i8237 {
 		}
 
 		void set_mode(uint8_t value) {
-			printf("DMA: Set mode %02x\n", value);
+//			printf("DMA: Set mode %02x\n", value);
 			channels_[value & 3].transfer = Channel::Transfer((value >> 2) & 3);
 			channels_[value & 3].autoinitialise = value & 0x10;
 			channels_[value & 3].address_decrement = value & 0x20;
@@ -209,7 +209,7 @@ class i8237 {
 		}
 
 		void set_command(uint8_t value) {
-			printf("DMA: Set command %02x\n", value);
+//			printf("DMA: Set command %02x\n", value);
 			enable_memory_to_memory_ = value & 0x01;
 			enable_channel0_address_hold_ = value & 0x02;
 			enable_controller_ = value & 0x04;

Machines/PCCompatible/MDA.hpp

@@ -90,7 +90,7 @@ class MDA {
 				// TODO: really this should be a Luminance8 and set an appropriate modal tint colour;
 				// consider whether that's worth building into the scan target.
 			{
-//				crt.set_visible_area(Outputs::Display::Rect(0.1072f, 0.1f, 0.842105263157895f, 0.842105263157895f));
+				crt.set_visible_area(Outputs::Display::Rect(0.028f, 0.025f, 0.98f, 0.98f));
 				crt.set_display_type(Outputs::Display::DisplayType::RGB);
 			}
 

Machines/PCCompatible/PCCompatible.cpp

@@ -113,14 +113,36 @@ class FloppyController {
 						printf("TODO: implement FDC command %d\n", uint8_t(decoder_.command()));
 					break;
 
-					case Command::ReadData: {
+					case Command::WriteDeletedData:
-						printf("FDC: Read from drive %d / head %d / track %d of head %d / track %d / sector %d\n",
+					case Command::WriteData: {
-							decoder_.target().drive,
+						status_.begin(decoder_);
-							decoder_.target().head,
+
-							drives_[decoder_.target().drive].track,
+						// Just decline to write, for now.
-							decoder_.geometry().head,
+						status_.set(Intel::i8272::Status1::NotWriteable);
+						status_.set(Intel::i8272::Status0::BecameNotReady);
+
+						results_.serialise(
+							status_,
 							decoder_.geometry().cylinder,
-							decoder_.geometry().sector);
+							decoder_.geometry().head,
+							decoder_.geometry().sector,
+							decoder_.geometry().size);
+
+						// TODO: what if head has changed?
+						drives_[decoder_.target().drive].status = decoder_.drive_head();
+						drives_[decoder_.target().drive].raised_interrupt = true;
+						pic_.apply_edge<6>(true);
+					} break;
+
+					case Command::ReadDeletedData:
+					case Command::ReadData: {
+//						printf("FDC: Read from drive %d / head %d / track %d of head %d / track %d / sector %d\n",
+//							decoder_.target().drive,
+//							decoder_.target().head,
+//							drives_[decoder_.target().drive].track,
+//							decoder_.geometry().head,
+//							decoder_.geometry().cylinder,
+//							decoder_.geometry().sector);
 
 						status_.begin(decoder_);
 
@@ -131,11 +153,13 @@ class FloppyController {
 							bool found_sector = false;
 
 							for(auto &pair: drives_[decoder_.target().drive].sectors(decoder_.target().head)) {
+								// TODO: I suspect that not all these fields are tested for equality.
 								if(
 									(pair.second.address.track == target.cylinder) &&
 									(pair.second.address.sector == target.sector) &&
 									(pair.second.address.side == target.head) &&
-									(pair.second.size == target.size)
+									(pair.second.size == target.size) &&
+									(pair.second.is_deleted == (decoder_.command() == Command::ReadDeletedData))
 								) {
 									found_sector = true;
 									bool wrote_in_full = true;
@@ -280,7 +304,7 @@ class FloppyController {
 
 	private:
 		void reset() {
-			printf("FDC reset\n");
+//			printf("FDC reset\n");
 			decoder_.clear();
 			status_.reset();
 
@@ -884,7 +908,7 @@ class FlowController {
 		bool halted_ = false;
 };
 
-template <VideoAdaptor video>
+template <VideoAdaptor video, bool turbo>
 class ConcreteMachine:
 	public Machine,
 	public MachineTypes::TimedMachine,
@@ -951,9 +975,15 @@ class ConcreteMachine:
 		// MARK: - TimedMachine.
 		void run_for(const Cycles duration) override {
 			const auto pit_ticks = duration.as_integral();
-			cpu_divisor_ += pit_ticks;
+
-			int ticks = cpu_divisor_ / 3;
+			int ticks;
-			cpu_divisor_ %= 3;
+			if constexpr (!turbo) {
+				cpu_divisor_ += pit_ticks;
+				ticks = cpu_divisor_ / 3;
+				cpu_divisor_ %= 3;
+			} else {
+				ticks = pit_ticks;
+			}
 
 			while(ticks--) {
 				//
@@ -965,23 +995,30 @@ class ConcreteMachine:
 				//
 				pit_.run_for(1);
 				++speaker_.cycles_since_update;
-				pit_.run_for(1);
+
-				++speaker_.cycles_since_update;
+				if constexpr (!turbo) {
-				pit_.run_for(1);
+					pit_.run_for(1);
-				++speaker_.cycles_since_update;
+					++speaker_.cycles_since_update;
+					pit_.run_for(1);
+					++speaker_.cycles_since_update;
+				}
 
 				//
 				// Advance CRTC at a more approximate rate.
 				//
-				video_.run_for(Cycles(3));
+				video_.run_for(turbo ? Cycles(1) : Cycles(3));
+
+				//
+				// Give the keyboard a notification of passing time; it's very approximately clocked,
+				// really just including 'some' delays to avoid being instant.
+				//
+				keyboard_.run_for(Cycles(1));
 
 				//
 				// Perform one CPU instruction every three PIT cycles.
 				// i.e. CPU instruction rate is 1/3 * ~1.19Mhz ~= 0.4 MIPS.
 				//
 
-				keyboard_.run_for(Cycles(1));
-
 				// Query for interrupts and apply if pending.
 				if(pic_.pending() && context.flags.template flag<InstructionSet::x86::Flag::Interrupt>()) {
 					// Regress the IP if a REP is in-progress so as to resume it later.
@@ -998,58 +1035,77 @@ class ConcreteMachine:
 					);
 				}
 
-				// Do nothing if halted.
+				// Do nothing if currently halted.
 				if(context.flow_controller.halted()) {
 					continue;
 				}
 
-				// Get the next thing to execute.
+				if constexpr (turbo) {
-				if(!context.flow_controller.should_repeat()) {
+					// There's no divider applied, so this makes for 2*PI = around 2.4 MIPS.
-					// Decode from the current IP.
+					// That's broadly 80286 speed, if MIPS were a valid measure.
-					decoded_ip_ = context.registers.ip();
+					perform_instruction();
-					const auto remainder = context.memory.next_code();
+					perform_instruction();
-					decoded = decoder.decode(remainder.first, remainder.second);
-
-					// If that didn't yield a whole instruction then the end of memory must have been hit;
-					// continue from the beginning.
-					if(decoded.first <= 0) {
-						const auto all = context.memory.all();
-						decoded = decoder.decode(all.first, all.second);
-					}
-
-					context.registers.ip() += decoded.first;
 				} else {
-					context.flow_controller.begin_instruction();
+					// With the clock divider above, this makes for a net of PIT/3 = around 0.4 MIPS.
+					// i.e. a shade more than 8086 speed, if MIPS were meaningful.
+					perform_instruction();
 				}
 
-/*				if(decoded_ip_ >= 0x7c00 && decoded_ip_ < 0x7c00 + 1024) {
+				// Other inevitably broad and fuzzy and inconsistent MIPS counts for my own potential future play:
-					const auto next = to_string(decoded, InstructionSet::x86::Model::i8086);
+				//
-//					if(next != previous) {
+				// 80386 @ 20Mhz: 4–5 MIPS.
-						std::cout << std::hex << decoded_ip_ << " " << next;
+				// 80486 @ 66Mhz: 25 MIPS.
-
+				// Pentium @ 100Mhz: 188 MIPS.
-						if(decoded.second.operation() == InstructionSet::x86::Operation::INT) {
-							std::cout << " dl:" << std::hex << +context.registers.dl() << "; ";
-							std::cout << "ah:" << std::hex << +context.registers.ah() << "; ";
-							std::cout << "ch:" << std::hex << +context.registers.ch() << "; ";
-							std::cout << "cl:" << std::hex << +context.registers.cl() << "; ";
-							std::cout << "dh:" << std::hex << +context.registers.dh() << "; ";
-							std::cout << "es:" << std::hex << +context.registers.es() << "; ";
-							std::cout << "bx:" << std::hex << +context.registers.bx();
-						}
-
-						std::cout << std::endl;
-//						previous = next;
-//					}
-				}*/
-
-				// Execute it.
-				InstructionSet::x86::perform(
-					decoded.second,
-					context
-				);
 			}
 		}
 
+		void perform_instruction() {
+			// Get the next thing to execute.
+			if(!context.flow_controller.should_repeat()) {
+				// Decode from the current IP.
+				decoded_ip_ = context.registers.ip();
+				const auto remainder = context.memory.next_code();
+				decoded = decoder.decode(remainder.first, remainder.second);
+
+				// If that didn't yield a whole instruction then the end of memory must have been hit;
+				// continue from the beginning.
+				if(decoded.first <= 0) {
+					const auto all = context.memory.all();
+					decoded = decoder.decode(all.first, all.second);
+				}
+
+				context.registers.ip() += decoded.first;
+			} else {
+				context.flow_controller.begin_instruction();
+			}
+
+/*			if(decoded_ip_ >= 0x7c00 && decoded_ip_ < 0x7c00 + 1024) {
+				const auto next = to_string(decoded, InstructionSet::x86::Model::i8086);
+//				if(next != previous) {
+					std::cout << std::hex << decoded_ip_ << " " << next;
+
+					if(decoded.second.operation() == InstructionSet::x86::Operation::INT) {
+						std::cout << " dl:" << std::hex << +context.registers.dl() << "; ";
+						std::cout << "ah:" << std::hex << +context.registers.ah() << "; ";
+						std::cout << "ch:" << std::hex << +context.registers.ch() << "; ";
+						std::cout << "cl:" << std::hex << +context.registers.cl() << "; ";
+						std::cout << "dh:" << std::hex << +context.registers.dh() << "; ";
+						std::cout << "es:" << std::hex << +context.registers.es() << "; ";
+						std::cout << "bx:" << std::hex << +context.registers.bx();
+					}
+
+					std::cout << std::endl;
+//					previous = next;
+//				}
+			}*/
+
+			// Execute it.
+			InstructionSet::x86::perform(
+				decoded.second,
+				context
+			);
+		}
+
 		// MARK: - ScanProducer.
 		void set_scan_target(Outputs::Display::ScanTarget *scan_target) override {
 			video_.set_scan_target(scan_target);
@@ -1109,10 +1165,9 @@ class ConcreteMachine:
 
 		void set_display_type(Outputs::Display::DisplayType display_type) override {
 			video_.set_display_type(display_type);
-			ppi_handler_.hint_is_composite(
+
-				(display_type == Outputs::Display::DisplayType::CompositeColour) ||
+			// Give the PPI a shout-out in case it isn't too late to switch to CGA40.
-				(display_type == Outputs::Display::DisplayType::CompositeMonochrome)
+			ppi_handler_.hint_is_composite(Outputs::Display::is_composite(display_type));
-			);
 		}
 
 		Outputs::Display::DisplayType get_display_type() const override {
@@ -1181,10 +1236,18 @@ Machine *Machine::PCCompatible(const Analyser::Static::Target *target, const ROM
 	using Target = Analyser::Static::PCCompatible::Target;
 	const Target *const pc_target = dynamic_cast<const Target *>(target);
 
-	switch(pc_target->adaptor) {
+	if(pc_target->speed == Target::Speed::Fast) {
-		case VideoAdaptor::MDA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::MDA>(*pc_target, rom_fetcher);
+		switch(pc_target->adaptor) {
-		case VideoAdaptor::CGA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::CGA>(*pc_target, rom_fetcher);
+			case VideoAdaptor::MDA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::MDA, true>(*pc_target, rom_fetcher);
-		default: return nullptr;
+			case VideoAdaptor::CGA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::CGA, true>(*pc_target, rom_fetcher);
+			default: return nullptr;
+		}
+	} else {
+		switch(pc_target->adaptor) {
+			case VideoAdaptor::MDA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::MDA, false>(*pc_target, rom_fetcher);
+			case VideoAdaptor::CGA:	return new PCCompatible::ConcreteMachine<VideoAdaptor::CGA, false>(*pc_target, rom_fetcher);
+			default: return nullptr;
+		}
 	}
 }
 

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -37,6 +37,8 @@
 		42A5E8532ABBE16F00A0DD5D /* lax_test.bin in Resources */ = {isa = PBXBuildFile; fileRef = 42A5E8422ABBE16F00A0DD5D /* lax_test.bin */; };
 		42A5E8542ABBE16F00A0DD5D /* branch_backwards_test.bin in Resources */ = {isa = PBXBuildFile; fileRef = 42A5E8432ABBE16F00A0DD5D /* branch_backwards_test.bin */; };
 		42E5C3932AC46A7700DA093D /* Carbon.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 42E5C3922AC46A7700DA093D /* Carbon.framework */; };
+		42EB81282B23AAC300429AF4 /* IMD.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 42EB81262B23AAC300429AF4 /* IMD.cpp */; };
+		42EB81292B23AAC300429AF4 /* IMD.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 42EB81262B23AAC300429AF4 /* IMD.cpp */; };
 		4B018B89211930DE002A3937 /* 65C02_extended_opcodes_test.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4B018B88211930DE002A3937 /* 65C02_extended_opcodes_test.bin */; };
 		4B01A6881F22F0DB001FD6E3 /* Z80MemptrTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B01A6871F22F0DB001FD6E3 /* Z80MemptrTests.swift */; };
 		4B0333AF2094081A0050B93D /* AppleDSK.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B0333AD2094081A0050B93D /* AppleDSK.cpp */; };
@@ -1195,6 +1197,8 @@
 		42AD55312A0C4D5000ACE410 /* 68000Implementation.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 68000Implementation.hpp; sourceTree = "<group>"; };
 		42E5C3922AC46A7700DA093D /* Carbon.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Carbon.framework; path = System/Library/Frameworks/Carbon.framework; sourceTree = SDKROOT; };
 		42EB81252B21788200429AF4 /* RTC.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = RTC.hpp; sourceTree = "<group>"; };
+		42EB81262B23AAC300429AF4 /* IMD.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = IMD.cpp; sourceTree = "<group>"; };
+		42EB81272B23AAC300429AF4 /* IMD.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = IMD.hpp; sourceTree = "<group>"; };
 		4B018B88211930DE002A3937 /* 65C02_extended_opcodes_test.bin */ = {isa = PBXFileReference; lastKnownFileType = archive.macbinary; name = 65C02_extended_opcodes_test.bin; path = "Klaus Dormann/65C02_extended_opcodes_test.bin"; sourceTree = "<group>"; };
 		4B01A6871F22F0DB001FD6E3 /* Z80MemptrTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Z80MemptrTests.swift; sourceTree = "<group>"; };
 		4B0333AD2094081A0050B93D /* AppleDSK.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = AppleDSK.cpp; sourceTree = "<group>"; };
@@ -3064,6 +3068,7 @@
 				4BEBFB4B2002C4BF000708CC /* FAT12.cpp */,
 				4B4518931F75FD1B00926311 /* G64.cpp */,
 				4B4518951F75FD1B00926311 /* HFE.cpp */,
+				42EB81262B23AAC300429AF4 /* IMD.cpp */,
 				4B5B372F2777C7FC0047F238 /* IPF.cpp */,
 				4BB4BFAE22A42F290069048D /* MacintoshIMG.cpp */,
 				4B58601C1F806AB200AEE2E3 /* MFMSectorDump.cpp */,
@@ -3084,6 +3089,7 @@
 				4BEBFB4C2002C4BF000708CC /* FAT12.hpp */,
 				4B4518941F75FD1B00926311 /* G64.hpp */,
 				4B4518961F75FD1B00926311 /* HFE.hpp */,
+				42EB81272B23AAC300429AF4 /* IMD.hpp */,
 				4B5B37302777C7FC0047F238 /* IPF.hpp */,
 				4BB4BFAF22A42F290069048D /* MacintoshIMG.hpp */,
 				4B58601D1F806AB200AEE2E3 /* MFMSectorDump.hpp */,
@@ -5959,6 +5965,7 @@
 				4B051C912669C90B00CA44E8 /* ROMCatalogue.cpp in Sources */,
 				4B055AB91FAE86170060FFFF /* Acorn.cpp in Sources */,
 				4B302185208A550100773308 /* DiskII.cpp in Sources */,
+				42EB81292B23AAC300429AF4 /* IMD.cpp in Sources */,
 				4B051CB1267C1CA200CA44E8 /* Keyboard.cpp in Sources */,
 				4B0F1BB32602645900B85C66 /* StaticAnalyser.cpp in Sources */,
 				4B055A931FAE85B50060FFFF /* BinaryDump.cpp in Sources */,
@@ -6057,6 +6064,7 @@
 				4B0333AF2094081A0050B93D /* AppleDSK.cpp in Sources */,
 				4B894518201967B4007DE474 /* ConfidenceCounter.cpp in Sources */,
 				4BCE005A227CFFCA000CA200 /* Macintosh.cpp in Sources */,
+				42EB81282B23AAC300429AF4 /* IMD.cpp in Sources */,
 				4B6AAEA4230E3E1D0078E864 /* MassStorageDevice.cpp in Sources */,
 				4B89452E201967B4007DE474 /* StaticAnalyser.cpp in Sources */,
 				4BC890D3230F86020025A55A /* DirectAccessDevice.cpp in Sources */,

OSBindings/Mac/Clock Signal/Info.plist

@@ -691,6 +691,26 @@
 			<key>NSDocumentClass</key>
 			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
 		</dict>
+		<dict>
+			<key>CFBundleTypeExtensions</key>
+			<array>
+				<string>imd</string>
+			</array>
+			<key>CFBundleTypeName</key>
+			<string>IMD disk image</string>
+			<key>CFBundleTypeOSTypes</key>
+			<array>
+				<string>????</string>
+			</array>
+			<key>CFBundleTypeRole</key>
+			<string>Viewer</string>
+			<key>LSHandlerRank</key>
+			<string>Owner</string>
+			<key>LSTypeIsPackage</key>
+			<false/>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
+		</dict>
 		<dict>
 			<key>CFBundleTypeExtensions</key>
 			<array>

OSBindings/Mac/Clock Signal/Machine/StaticAnalyser/CSStaticAnalyser.h

@@ -123,8 +123,9 @@ typedef NS_ENUM(NSInteger, CSMachineMSXRegion) {
 	CSMachineMSXRegionJapanese,
 };
 
-typedef NS_ENUM(NSInteger, CSPCCompatibleModel) {
+typedef NS_ENUM(NSInteger, CSPCCompatibleSpeed) {
-	CSPCCompatibleModelTurboXT,
+	CSPCCompatibleSpeedOriginal,
+	CSPCCompatibleSpeedTurbo,
 };
 
 typedef NS_ENUM(NSInteger, CSPCCompatibleVideoAdaptor) {
@@ -152,7 +153,7 @@ typedef int Kilobytes;
 - (instancetype)initWithVic20Region:(CSMachineVic20Region)region memorySize:(Kilobytes)memorySize hasC1540:(BOOL)hasC1540;
 - (instancetype)initWithZX80MemorySize:(Kilobytes)memorySize useZX81ROM:(BOOL)useZX81ROM;
 - (instancetype)initWithZX81MemorySize:(Kilobytes)memorySize;
-- (instancetype)initWithPCCompatibleModel:(CSPCCompatibleModel)model videoAdaptor:(CSPCCompatibleVideoAdaptor)adaptor;
+- (instancetype)initWithPCCompatibleSpeed:(CSPCCompatibleSpeed)speed videoAdaptor:(CSPCCompatibleVideoAdaptor)adaptor;
 
 @property(nonatomic, readonly, nullable) NSString *optionsNibName;
 @property(nonatomic, readonly) NSString *displayName;

OSBindings/Mac/Clock Signal/Machine/StaticAnalyser/CSStaticAnalyser.mm

@@ -273,7 +273,7 @@
 	return self;
 }
 
-- (instancetype)initWithPCCompatibleModel:(CSPCCompatibleModel)model videoAdaptor:(CSPCCompatibleVideoAdaptor)adaptor {
+- (instancetype)initWithPCCompatibleSpeed:(CSPCCompatibleSpeed)speed videoAdaptor:(CSPCCompatibleVideoAdaptor)adaptor {
 	self = [super init];
 	if(self) {
 		using Target = Analyser::Static::PCCompatible::Target;
@@ -282,6 +282,10 @@
 			case CSPCCompatibleVideoAdaptorMDA:	target->adaptor = Target::VideoAdaptor::MDA;	break;
 			case CSPCCompatibleVideoAdaptorCGA:	target->adaptor = Target::VideoAdaptor::CGA;	break;
 		}
+		switch(speed) {
+			case CSPCCompatibleSpeedOriginal:	target->speed = Target::Speed::ApproximatelyOriginal;	break;
+			case CSPCCompatibleSpeedTurbo:		target->speed = Target::Speed::Fast;					break;
+		}
 		_targets.push_back(std::move(target));
 	}
 	return self;

OSBindings/Mac/Clock Signal/MachinePicker/Base.lproj/MachinePicker.xib

@@ -750,13 +750,39 @@ Gw
                                                 <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                                             </textFieldCell>
                                         </textField>
+                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="8vF-eu-ClP">
+                                            <rect key="frame" x="18" y="168" width="47" height="16"/>
+                                            <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" title="Speed:" id="qXc-wf-5jm">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <popUpButton verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="Ci6-TG-5tW">
+                                            <rect key="frame" x="68" y="162" width="146" height="25"/>
+                                            <popUpButtonCell key="cell" type="push" title="Similar to Original" bezelStyle="rounded" alignment="left" lineBreakMode="truncatingTail" state="on" borderStyle="borderAndBezel" tag="8086" imageScaling="axesIndependently" inset="2" selectedItem="R4W-s4-KFx" id="9i0-UG-B2c">
+                                                <behavior key="behavior" lightByBackground="YES" lightByGray="YES"/>
+                                                <font key="font" metaFont="menu"/>
+                                                <menu key="menu" id="KQw-8g-SrI">
+                                                    <items>
+                                                        <menuItem title="Similar to Original" state="on" tag="8086" id="R4W-s4-KFx"/>
+                                                        <menuItem title="Turbo" tag="80286" id="LeD-N4-avf"/>
+                                                    </items>
+                                                </menu>
+                                            </popUpButtonCell>
+                                        </popUpButton>
                                     </subviews>
                                     <constraints>
+                                        <constraint firstItem="Ci6-TG-5tW" firstAttribute="leading" secondItem="8vF-eu-ClP" secondAttribute="trailing" constant="8" symbolic="YES" id="0Sb-TO-UVM"/>
+                                        <constraint firstItem="Ci6-TG-5tW" firstAttribute="top" secondItem="stw-i3-ikG" secondAttribute="bottom" constant="10" symbolic="YES" id="4E9-4l-fat"/>
+                                        <constraint firstAttribute="bottom" relation="greaterThanOrEqual" secondItem="Ci6-TG-5tW" secondAttribute="bottom" constant="20" symbolic="YES" id="9C6-PK-12w"/>
                                         <constraint firstAttribute="trailing" relation="greaterThanOrEqual" secondItem="stw-i3-ikG" secondAttribute="trailing" constant="20" symbolic="YES" id="A0n-lr-LHf"/>
+                                        <constraint firstAttribute="trailing" relation="greaterThanOrEqual" secondItem="Ci6-TG-5tW" secondAttribute="trailing" constant="20" symbolic="YES" id="G4D-zS-Q1t"/>
                                         <constraint firstItem="uhf-1k-ibT" firstAttribute="leading" secondItem="gJD-vd-WWu" secondAttribute="leading" constant="20" symbolic="YES" id="JNr-Tg-gDV"/>
-                                        <constraint firstAttribute="bottom" relation="greaterThanOrEqual" secondItem="stw-i3-ikG" secondAttribute="bottom" constant="20" symbolic="YES" id="RSc-OQ-KNO"/>
                                         <constraint firstItem="uhf-1k-ibT" firstAttribute="centerY" secondItem="stw-i3-ikG" secondAttribute="centerY" id="bfD-kx-eOc"/>
                                         <constraint firstItem="stw-i3-ikG" firstAttribute="leading" secondItem="uhf-1k-ibT" secondAttribute="trailing" constant="8" symbolic="YES" id="f6l-B2-nBw"/>
+                                        <constraint firstItem="8vF-eu-ClP" firstAttribute="leading" secondItem="gJD-vd-WWu" secondAttribute="leading" constant="20" symbolic="YES" id="ftj-Es-CRQ"/>
+                                        <constraint firstItem="8vF-eu-ClP" firstAttribute="centerY" secondItem="Ci6-TG-5tW" secondAttribute="centerY" id="wUL-sD-fae"/>
                                         <constraint firstItem="stw-i3-ikG" firstAttribute="top" secondItem="gJD-vd-WWu" secondAttribute="top" constant="20" symbolic="YES" id="wjD-TM-5CL"/>
                                     </constraints>
                                 </view>
@@ -1069,6 +1095,7 @@ Gw
                 <outlet property="msxRegionButton" destination="LG6-mP-SeG" id="3a9-VG-6Wf"/>
                 <outlet property="oricDiskInterfaceButton" destination="fYL-p6-wyn" id="aAt-wM-hRZ"/>
                 <outlet property="oricModelTypeButton" destination="ENP-hI-BVZ" id="n9i-Ym-miE"/>
+                <outlet property="pcSpeedButton" destination="Ci6-TG-5tW" id="34Y-5H-5dN"/>
                 <outlet property="pcVideoAdaptorButton" destination="stw-i3-ikG" id="6VO-Q9-4kV"/>
                 <outlet property="spectrumModelTypeButton" destination="gFZ-d4-WFv" id="tdX-Cv-Swe"/>
                 <outlet property="vic20HasC1540Button" destination="Lrf-gL-6EI" id="21g-dJ-mOo"/>

OSBindings/Mac/Clock Signal/MachinePicker/MachinePicker.swift

@@ -65,6 +65,7 @@ class MachinePicker: NSObject, NSTableViewDataSource, NSTableViewDelegate {
 
 	// MARK: - PC compatible properties
 	@IBOutlet var pcVideoAdaptorButton: NSPopUpButton!
+	@IBOutlet var pcSpeedButton: NSPopUpButton!
 
 	// MARK: - Spectrum properties
 	@IBOutlet var spectrumModelTypeButton: NSPopUpButton!
@@ -155,6 +156,7 @@ class MachinePicker: NSObject, NSTableViewDataSource, NSTableViewDelegate {
 
 		// PC settings
 		pcVideoAdaptorButton.selectItem(withTag: standardUserDefaults.integer(forKey: "new.pcVideoAdaptor"))
+		pcSpeedButton.selectItem(withTag: standardUserDefaults.integer(forKey: "new.pcSpeed"))
 
 		// Spectrum settings
 		spectrumModelTypeButton.selectItem(withTag: standardUserDefaults.integer(forKey: "new.spectrumModel"))
@@ -224,6 +226,7 @@ class MachinePicker: NSObject, NSTableViewDataSource, NSTableViewDelegate {
 
 		// PC settings
 		standardUserDefaults.set(pcVideoAdaptorButton.selectedTag(), forKey: "new.pcVideoAdaptor")
+		standardUserDefaults.set(pcSpeedButton.selectedTag(), forKey: "new.pcSpeed")
 
 		// Spectrum settings
 		standardUserDefaults.set(spectrumModelTypeButton.selectedTag(), forKey: "new.spectrumModel")
@@ -416,7 +419,12 @@ class MachinePicker: NSObject, NSTableViewDataSource, NSTableViewDelegate {
 					case 1:		videoAdaptor = .CGA
 					default:	break
 				}
-				return CSStaticAnalyser(pcCompatibleModel: .turboXT, videoAdaptor: videoAdaptor)
+				var speed: CSPCCompatibleSpeed = .original
+				switch pcSpeedButton.selectedTag() {
+					case 80286:	speed = .turbo
+					default:	break
+				}
+				return CSStaticAnalyser(pcCompatibleSpeed: speed, videoAdaptor: videoAdaptor)
 
 			case "spectrum":
 				var model: CSMachineSpectrumModel = .plus2a

Outputs/ScanTarget.hpp

@@ -51,6 +51,10 @@ enum class DisplayType {
 	CompositeMonochrome
 };
 
+constexpr bool is_composite(DisplayType type) {
+	return type == DisplayType::CompositeColour || type == DisplayType::CompositeMonochrome;
+}
+
 /*!
 	Enumerates the potential formats of input data.
 

Storage/Disk/DiskImage/Formats/CPCDSK.hpp

@@ -24,19 +24,18 @@ namespace Storage::Disk {
 class CPCDSK: public DiskImage {
 	public:
 		/*!
-			Construct an @c AcornADF containing content from the file with name @c file_name.
+			Construct a @c CPCDSK containing content from the file with name @c file_name.
 
 			@throws Storage::FileHolder::Error::CantOpen if this file can't be opened.
 			@throws Error::InvalidFormat if the file doesn't appear to contain an Acorn .ADF format image.
 		*/
 		CPCDSK(const std::string &file_name);
 
-		// implemented to satisfy @c Disk
+		// DiskImage interface.
 		HeadPosition get_maximum_head_position() final;
 		int get_head_count() final;
 		bool get_is_read_only() final;
-
+		void set_tracks(const std::map<::Storage::Disk::Track::Address, std::shared_ptr<::Storage::Disk::Track>> &tracks) final;
-		void set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) final;
 		std::shared_ptr<::Storage::Disk::Track> get_track_at_position(::Storage::Disk::Track::Address address) final;
 
 	private:

Storage/Disk/DiskImage/Formats/IMD.cpp

@@ -0,0 +1,163 @@
+//
+//  IMD.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 08/12/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#include "IMD.hpp"
+
+#include "../../Encodings/MFM/Constants.hpp"
+#include "../../Encodings/MFM/Encoder.hpp"
+#include "../../Encodings/MFM/SegmentParser.hpp"
+#include "../../Track/TrackSerialiser.hpp"
+
+#include <algorithm>
+
+using namespace Storage::Disk;
+
+// Documentation source: https://oldcomputers-ddns.org/public/pub/manuals/imd.pdf
+
+IMD::IMD(const std::string &file_name) : file_(file_name) {
+	// Check for signature.
+	if(!file_.check_signature("IMD")) {
+		throw Error::InvalidFormat;
+	}
+
+	// Skip rest of ASCII.
+	while(file_.get8() != 0x1a);
+
+	// Build track map.
+	while(true) {
+		const auto location = file_.tell();
+
+		// Skip mode.
+		file_.seek(1, SEEK_CUR);
+
+		// Grab relevant fields.
+		const uint8_t cylinder = file_.get8();
+		const uint8_t head = file_.get8();
+		const uint8_t sector_count = file_.get8();
+		const uint8_t sector_size = file_.get8();
+		if(file_.eof()) {
+			break;
+		}
+
+		cylinders_ = std::max(cylinder, cylinders_);
+		heads_ = std::max(uint8_t(head & 1), heads_);
+
+		// Update head and cylinder extents, record sector location for later.
+		track_locations_.emplace(
+			Storage::Disk::Track::Address(head & 1, HeadPosition(cylinder)),
+			location);
+
+		// Skip sector numbers.
+		file_.seek(sector_count, SEEK_CUR);
+
+		// Skip cylinder map.
+		if(head & 0x80) {
+			file_.seek(sector_count, SEEK_CUR);
+		}
+
+		// Skip head map.
+		if(head & 0x40) {
+			file_.seek(sector_count, SEEK_CUR);
+		}
+
+		// Skip sectors.
+		for(int c = 0; c < sector_count; c++) {
+			const uint8_t type = file_.get8();
+			switch(type) {
+				case 0x00:	break;	// Sector couldn't be read.
+
+				// Types with all sector data present.
+				case 0x01:	case 0x03:	case 0x05:	case 0x07:
+					file_.seek(128 << sector_size, SEEK_CUR);
+				break;
+
+				// Types with a single byte present.
+				case 0x02:	case 0x04:	case 0x06:	case 0x08:
+					file_.seek(1, SEEK_CUR);
+				break;
+			}
+		}
+	}
+
+	// Both heads_ and cylinders_ are now the maximum observed IDs, which
+	// are one less than the counts.
+	++ cylinders_;
+	++ heads_;
+}
+
+HeadPosition IMD::get_maximum_head_position() {
+	return HeadPosition(cylinders_);
+}
+
+int IMD::get_head_count() {
+	return heads_ + 1;
+}
+
+std::shared_ptr<::Storage::Disk::Track> IMD::get_track_at_position(::Storage::Disk::Track::Address address) {
+	auto location = track_locations_.find(address);
+	if(location == track_locations_.end()) {
+		return nullptr;
+	}
+
+	// Seek to track, parse fully this time.
+	file_.seek(location->second, SEEK_SET);
+
+	const uint8_t mode = file_.get8();
+	const uint8_t cylinder = file_.get8();
+	const uint8_t head = file_.get8();
+	const uint8_t sector_count = file_.get8();
+	const uint8_t sector_size = file_.get8();
+
+	const std::vector<uint8_t> sector_ids = file_.read(sector_count);
+	const std::vector<uint8_t> cylinders = (head & 0x80) ? file_.read(sector_count) : std::vector<uint8_t>{};
+	const std::vector<uint8_t> heads = (head & 0x40) ? file_.read(sector_count) : std::vector<uint8_t>{};
+
+	std::vector<Storage::Encodings::MFM::Sector> sectors;
+	sectors.reserve(sector_count);
+
+	for(size_t c = 0; c < sector_count; c++) {
+		sectors.emplace_back();
+		Storage::Encodings::MFM::Sector &sector = sectors.back();
+
+		// Set up sector address.
+		sector.address.track = cylinders.empty() ? cylinder : cylinders[c];
+		sector.address.side = heads.empty() ? head & 1 : heads[c];
+		sector.address.sector = sector_ids[c];
+		sector.size = sector_size;
+
+		const auto byte_size = size_t(128 << sector_size);
+		uint8_t type = file_.get8();
+
+		// Type 0: sector was present, but couldn't be read.
+		// Since body CRC errors are a separate item, just don't include a body at all.
+		if(!type) {
+			continue;
+		}
+
+		// Decrement type to turn it into a bit field:
+		//
+		//	b0 => is compressed within disk image;
+		//	b1 => had deleted address mark;
+		//	b2 => had data CRC error.
+		--type;
+		sector.is_deleted = type & 2;
+		sector.has_data_crc_error = type & 4;
+		if(type & 1) {
+			sector.samples.emplace_back(byte_size, file_.get8());
+		} else {
+			sector.samples.push_back(file_.read(byte_size));
+		}
+	}
+
+	// Mode also indicates data density, but I don't have a good strategy for reconciling that if
+	// it were to disagree with the density implied by the quantity of sectors. So a broad 'is it MFM' test is
+	// applied only.
+	return (mode >= 3) ?
+		Storage::Encodings::MFM::GetMFMTrackWithSectors(sectors) :
+		Storage::Encodings::MFM::GetFMTrackWithSectors(sectors);
+}

Storage/Disk/DiskImage/Formats/IMD.hpp

@@ -0,0 +1,45 @@
+//
+//  IMD.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 08/12/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef IMD_hpp
+#define IMD_hpp
+
+#include "../DiskImage.hpp"
+#include "../../../FileHolder.hpp"
+
+namespace Storage::Disk {
+
+/*!
+	Provides an @c DiskImage containing an IMD image, which is a collection of arbitrarily-numbered FM or MFM
+	sectors collected by track.
+*/
+
+class IMD: public DiskImage {
+	public:
+		/*!
+			Construct an @c IMD containing content from the file with name @c file_name.
+
+			@throws Storage::FileHolder::Error::CantOpen if this file can't be opened.
+			@throws Error::InvalidFormat if the file doesn't appear to contain an Acorn .ADF format image.
+		*/
+		IMD(const std::string &file_name);
+
+		// DiskImage interface.
+		HeadPosition get_maximum_head_position() final;
+		int get_head_count() final;
+		std::shared_ptr<::Storage::Disk::Track> get_track_at_position(::Storage::Disk::Track::Address address) final;
+
+	private:
+		FileHolder file_;
+		std::map<Storage::Disk::Track::Address, long> track_locations_;
+		uint8_t cylinders_ = 0, heads_ = 0;
+};
+
+}
+
+#endif /* IMD_hpp */