diff --git a/Machines/PCCompatible/PCCompatible.cpp b/Machines/PCCompatible/PCCompatible.cpp
index 2a42c0a34..fae9e7147 100644
--- a/Machines/PCCompatible/PCCompatible.cpp
+++ b/Machines/PCCompatible/PCCompatible.cpp
@@ -8,6 +8,8 @@
 
 #include "PCCompatible.hpp"
 
+#include "PIT.hpp"
+
 #include "../../InstructionSets/x86/Decoder.hpp"
 #include "../../InstructionSets/x86/Flags.hpp"
 #include "../../InstructionSets/x86/Instruction.hpp"
@@ -82,6 +84,10 @@ class PIC {
 			return 0;
 		}
 
+		template <int vector>
+		void raise() {
+		}
+
 	private:
 		bool single_pic_ = false;
 		bool four_byte_vectors_ = false;
@@ -197,199 +203,6 @@ class DMA {
 		} channels_[4];
 };
 
-template <bool is_8254>
-class PIT {
-	public:
-		template <int channel> uint8_t read() {
-			const auto result = channels_[channel].read();
-			printf("PIT: read from %d; %02x\n", channel, result);
-			return result;
-		}
-
-		template <int channel> void write(uint8_t value) {
-			printf("PIT: write to %d\n", channel);
-			channels_[channel].write(value);
-		}
-
-		void set_mode(uint8_t value) {
-			const int channel_id = (value >> 6) & 3;
-			if(channel_id == 3) {
-				read_back_ = is_8254;
-
-				// TODO: decode rest of read-back command.
-				return;
-			}
-
-			printf("PIT: set mode on %d\n", channel_id);
-
-			Channel &channel = channels_[channel_id];
-			switch((value >> 4) & 3) {
-				default:
-					channel.latch_value();
-				return;
-
-				case 1:		channel.latch_mode = LatchMode::LowOnly;	break;
-				case 2:		channel.latch_mode = LatchMode::HighOnly;	break;
-				case 3:		channel.latch_mode = LatchMode::LowHigh;	break;
-			}
-			channel.is_bcd = value & 1;
-			channel.next_access_high = false;
-
-			const auto operating_mode = (value >> 1) & 7;
-			switch(operating_mode) {
-				default:	channel.mode = OperatingMode(operating_mode);		break;
-				case 6:		channel.mode = OperatingMode::RateGenerator;		break;
-				case 7:		channel.mode = OperatingMode::SquareWaveGenerator;	break;
-			}
-
-			// Set up operating mode.
-			switch(channel.mode) {
-				default:
-					printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
-				break;
-
-				case OperatingMode::InterruptOnTerminalCount:
-					channel.output = false;
-					channel.awaiting_reload = true;
-				break;
-
-				case OperatingMode::RateGenerator:
-					channel.output = true;
-					channel.awaiting_reload = true;
-				break;
-			}
-		}
-
-		void run_for(Cycles cycles) {
-			// TODO: be intelligent enough to take ticks outside the loop when appropriate.
-			auto ticks = cycles.as<int>();
-			while(ticks--) {
-				bool output_changed;
-				output_changed = channels_[0].advance(1);
-				output_changed |= channels_[1].advance(1);
-				output_changed |= channels_[2].advance(1);
-			}
-		}
-
-	private:
-		// Supported only on 8254s.
-		bool read_back_ = false;
-
-		enum class LatchMode {
-			LowOnly,
-			HighOnly,
-			LowHigh,
-		};
-
-		enum class OperatingMode {
-			InterruptOnTerminalCount		= 0,
-			HardwareRetriggerableOneShot	= 1,
-			RateGenerator					= 2,
-			SquareWaveGenerator				= 3,
-			SoftwareTriggeredStrobe			= 4,
-			HardwareTriggeredStrobe			= 5,
-		};
-
-		struct Channel {
-			LatchMode latch_mode = LatchMode::LowHigh;
-			OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
-			bool is_bcd = false;
-
-			bool gated = false;
-			bool awaiting_reload = true;
-
-			uint16_t counter = 0;
-			uint16_t reload = 0;
-			uint16_t latch = 0;
-			bool output = false;
-
-			bool next_access_high = false;
-
-			void latch_value() {
-				latch = counter;
-			}
-
-			bool advance(int ticks) {
-				if(gated || awaiting_reload) return false;
-
-				// TODO: BCD mode is completely ignored below. Possibly not too important.
-				const bool initial_output = output;
-				switch(mode) {
-					case OperatingMode::InterruptOnTerminalCount:
-						// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
-						output |= counter <= ticks;
-						counter -= ticks;
-					break;
-
-					case OperatingMode::RateGenerator:
-						// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
-						if(counter <= ticks) {
-							counter = reload - ticks + counter;
-						} else {
-							counter -= ticks;
-						}
-						output = counter != 1;
-					break;
-
-					default:
-						// TODO.
-						break;
-				}
-
-				return output != initial_output;
-			}
-
-			void write(uint8_t value) {
-				switch(latch_mode) {
-					case LatchMode::LowOnly:
-						reload = (reload & 0xff00) | value;
-					break;
-					case LatchMode::HighOnly:
-						reload = uint16_t((reload & 0x00ff) | (value << 8));
-					break;
-					case LatchMode::LowHigh:
-						next_access_high ^= true;
-						if(next_access_high) {
-							reload = (reload & 0xff00) | value;
-							return;
-						}
-
-						reload = uint16_t((reload & 0x00ff) | (value << 8));
-					break;
-				}
-
-				awaiting_reload = false;
-
-				switch(mode) {
-					case OperatingMode::InterruptOnTerminalCount:
-					case OperatingMode::RateGenerator:
-						counter = reload;
-					break;
-				}
-			}
-
-			uint8_t read() {
-				switch(latch_mode) {
-					case LatchMode::LowOnly:	return uint8_t(latch);
-					case LatchMode::HighOnly:	return uint8_t(latch >> 8);
-					default:
-					case LatchMode::LowHigh:
-						next_access_high ^= true;
-						return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
-					break;
-				}
-			}
-		} channels_[3];
-
-		// TODO:
-		//
-		//	channel 0 is connected to IRQ 0;
-		//	channel 1 is used for DRAM refresh;
-		//	channel 2 is gated by a PPI output and feeds into the speaker.
-		//
-		//	RateGenerator: output goes high if gated.
-};
-
 struct Registers {
 	public:
 		static constexpr bool is_32bit = false;
diff --git a/Machines/PCCompatible/PIT.hpp b/Machines/PCCompatible/PIT.hpp
new file mode 100644
index 000000000..ec3126618
--- /dev/null
+++ b/Machines/PCCompatible/PIT.hpp
@@ -0,0 +1,209 @@
+//
+//  PIT.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 20/11/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef PIT_hpp
+#define PIT_hpp
+
+namespace PCCompatible {
+
+template <bool is_8254>
+class PIT {
+	public:
+		template <int channel> uint8_t read() {
+			const auto result = channels_[channel].read();
+			printf("PIT: read from %d; %02x\n", channel, result);
+			return result;
+		}
+
+		template <int channel> void write(uint8_t value) {
+			printf("PIT: write to %d\n", channel);
+			channels_[channel].write(value);
+		}
+
+		void set_mode(uint8_t value) {
+			const int channel_id = (value >> 6) & 3;
+			if(channel_id == 3) {
+				read_back_ = is_8254;
+
+				// TODO: decode rest of read-back command.
+				return;
+			}
+
+			printf("PIT: set mode on %d\n", channel_id);
+
+			Channel &channel = channels_[channel_id];
+			switch((value >> 4) & 3) {
+				default:
+					channel.latch_value();
+				return;
+
+				case 1:		channel.latch_mode = LatchMode::LowOnly;	break;
+				case 2:		channel.latch_mode = LatchMode::HighOnly;	break;
+				case 3:		channel.latch_mode = LatchMode::LowHigh;	break;
+			}
+			channel.is_bcd = value & 1;
+			channel.next_access_high = false;
+
+			const auto operating_mode = (value >> 1) & 7;
+			switch(operating_mode) {
+				default:	channel.mode = OperatingMode(operating_mode);		break;
+				case 6:		channel.mode = OperatingMode::RateGenerator;		break;
+				case 7:		channel.mode = OperatingMode::SquareWaveGenerator;	break;
+			}
+
+			// Set up operating mode.
+			switch(channel.mode) {
+				default:
+					printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
+				break;
+
+				case OperatingMode::InterruptOnTerminalCount:
+					channel.output = false;
+					channel.awaiting_reload = true;
+				break;
+
+				case OperatingMode::RateGenerator:
+					channel.output = true;
+					channel.awaiting_reload = true;
+				break;
+			}
+		}
+
+		void run_for(Cycles cycles) {
+			// TODO: be intelligent enough to take ticks outside the loop when appropriate.
+			auto ticks = cycles.as<int>();
+			while(ticks--) {
+				bool output_changed;
+				output_changed = channels_[0].advance(1);
+				output_changed |= channels_[1].advance(1);
+				output_changed |= channels_[2].advance(1);
+			}
+		}
+
+	private:
+		// Supported only on 8254s.
+		bool read_back_ = false;
+
+		enum class LatchMode {
+			LowOnly,
+			HighOnly,
+			LowHigh,
+		};
+
+		enum class OperatingMode {
+			InterruptOnTerminalCount		= 0,
+			HardwareRetriggerableOneShot	= 1,
+			RateGenerator					= 2,
+			SquareWaveGenerator				= 3,
+			SoftwareTriggeredStrobe			= 4,
+			HardwareTriggeredStrobe			= 5,
+		};
+
+		struct Channel {
+			LatchMode latch_mode = LatchMode::LowHigh;
+			OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
+			bool is_bcd = false;
+
+			bool gated = false;
+			bool awaiting_reload = true;
+
+			uint16_t counter = 0;
+			uint16_t reload = 0;
+			uint16_t latch = 0;
+			bool output = false;
+
+			bool next_access_high = false;
+
+			void latch_value() {
+				latch = counter;
+			}
+
+			bool advance(int ticks) {
+				if(gated || awaiting_reload) return false;
+
+				// TODO: BCD mode is completely ignored below. Possibly not too important.
+				const bool initial_output = output;
+				switch(mode) {
+					case OperatingMode::InterruptOnTerminalCount:
+						// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
+						output |= counter <= ticks;
+						counter -= ticks;
+					break;
+
+					case OperatingMode::RateGenerator:
+						// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
+						if(counter <= ticks) {
+							counter = reload - ticks + counter;
+						} else {
+							counter -= ticks;
+						}
+						output = counter != 1;
+					break;
+
+					default:
+						// TODO.
+						break;
+				}
+
+				return output != initial_output;
+			}
+
+			void write(uint8_t value) {
+				switch(latch_mode) {
+					case LatchMode::LowOnly:
+						reload = (reload & 0xff00) | value;
+					break;
+					case LatchMode::HighOnly:
+						reload = uint16_t((reload & 0x00ff) | (value << 8));
+					break;
+					case LatchMode::LowHigh:
+						next_access_high ^= true;
+						if(next_access_high) {
+							reload = (reload & 0xff00) | value;
+							return;
+						}
+
+						reload = uint16_t((reload & 0x00ff) | (value << 8));
+					break;
+				}
+
+				awaiting_reload = false;
+
+				switch(mode) {
+					case OperatingMode::InterruptOnTerminalCount:
+					case OperatingMode::RateGenerator:
+						counter = reload;
+					break;
+				}
+			}
+
+			uint8_t read() {
+				switch(latch_mode) {
+					case LatchMode::LowOnly:	return uint8_t(latch);
+					case LatchMode::HighOnly:	return uint8_t(latch >> 8);
+					default:
+					case LatchMode::LowHigh:
+						next_access_high ^= true;
+						return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
+					break;
+				}
+			}
+		} channels_[3];
+
+		// TODO:
+		//
+		//	channel 0 is connected to IRQ 0;
+		//	channel 1 is used for DRAM refresh;
+		//	channel 2 is gated by a PPI output and feeds into the speaker.
+		//
+		//	RateGenerator: output goes high if gated.
+};
+
+}
+
+#endif /* PIT_hpp */
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index bb8eb4145..45be4a9f8 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -1142,6 +1142,7 @@
 		425739302AFBE47700B7D1E4 /* InOut.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = InOut.hpp; sourceTree = "<group>"; };
 		425739362B051EA800B7D1E4 /* PCCompatible.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = PCCompatible.hpp; sourceTree = "<group>"; };
 		425739372B051EA800B7D1E4 /* PCCompatible.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PCCompatible.cpp; sourceTree = "<group>"; };
+		4267A9C72B0C26FA008A59BB /* PIT.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = PIT.hpp; sourceTree = "<group>"; };
 		4281572E2AA0334300E16AA1 /* Carry.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Carry.hpp; sourceTree = "<group>"; };
 		428168372A16C25C008ECD27 /* LineLayout.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = LineLayout.hpp; sourceTree = "<group>"; };
 		428168392A37AFB4008ECD27 /* DispatcherTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = DispatcherTests.mm; sourceTree = "<group>"; };
@@ -2360,8 +2361,9 @@
 		425739352B051EA800B7D1E4 /* PCCompatible */ = {
 			isa = PBXGroup;
 			children = (
-				425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
 				425739372B051EA800B7D1E4 /* PCCompatible.cpp */,
+				425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
+				4267A9C72B0C26FA008A59BB /* PIT.hpp */,
 			);
 			path = PCCompatible;
 			sourceTree = "<group>";