diff --git a/Machines/Atari2600/Atari2600.cpp b/Machines/Atari2600/Atari2600.cpp
index 835352a92..e479780f5 100644
--- a/Machines/Atari2600/Atari2600.cpp
+++ b/Machines/Atari2600/Atari2600.cpp
@@ -11,7 +11,9 @@
 #include <stdio.h>
 
 using namespace Atari2600;
-static const int horizontalTimerReload = 227;
+namespace {
+	static const unsigned int horizontalTimerPeriod = 228;
+}
 
 Machine::Machine() :
 	_horizontalTimer(0),
@@ -19,12 +21,39 @@ Machine::Machine() :
 	_lastOutputState(OutputState::Sync),
 	_piaTimerStatus(0xff),
 	_rom(nullptr),
-	_hMoveWillCount(false),
 	_piaDataValue{0xff, 0xff},
-	_tiaInputValue{0xff, 0xff}
+	_tiaInputValue{0xff, 0xff},
+	_upcomingEventsPointer(0),
+	_objectCounterPointer(0),
+	_stateByTime(_stateByExtendTime[0]),
+	_cycles_since_speaker_update(0)
 {
 	memset(_collisions, 0xff, sizeof(_collisions));
 	set_reset_line(true);
+	setup_reported_collisions();
+
+	for(int vbextend = 0; vbextend < 2; vbextend++)
+	{
+		for(int c = 0; c < 57; c++)
+		{
+			OutputState state;
+
+			// determine which output state will be active in four cycles from now
+			switch(c)
+			{
+				case 0: case 1: case 2: case 3:					state = OutputState::Blank;									break;
+				case 4: case 5: case 6: case 7:					state = OutputState::Sync;									break;
+				case 8: case 9: case 10: case 11:				state = OutputState::ColourBurst;							break;
+				case 12: case 13: case 14:
+				case 15: case 16:								state = OutputState::Blank;									break;
+
+				case 17: case 18:								state = vbextend ? OutputState::Blank : OutputState::Pixel;	break;
+				default:										state = OutputState::Pixel;									break;
+			}
+
+			_stateByExtendTime[vbextend][c] = state;
+		}
+	}
 }
 
 void Machine::setup_output(float aspect_ratio)
@@ -43,6 +72,8 @@ void Machine::setup_output(float aspect_ratio)
 			"return (float(y) / 14.0) * (1.0 - amplitude) + step(1, iPhase) * amplitude * cos(phase + phaseOffset);"
 		"}");
 	_crt->set_output_device(Outputs::CRT::Television);
+
+	_speaker.set_input_rate(1194720 / 38);
 }
 
 void Machine::switch_region()
@@ -61,6 +92,8 @@ void Machine::switch_region()
 			"return (float(y) / 14.0) * (1.0 - amplitude) + step(4, (iPhase + 2u) & 15u) * amplitude * cos(phase + phaseOffset);"
 		"}");
 	_crt->set_new_timing(228, 312, Outputs::CRT::ColourSpace::YUV, 228, 1);
+
+//	_speaker.set_input_rate(2 * 312 * 50);
 }
 
 void Machine::close_output()
@@ -75,96 +108,133 @@ Machine::~Machine()
 	close_output();
 }
 
-void Machine::get_output_pixel(uint8_t *pixel, int offset)
+void Machine::update_timers(int mask)
 {
-	// get the playfield pixel and hence a proposed colour
-	uint8_t playfieldPixel = _playfield[offset >> 2];
-	uint8_t playfieldColour = ((_playfieldControl&6) == 2) ? _playerColour[offset / 80] : _playfieldColour;
+	unsigned int upcomingPointerPlus4 = (_upcomingEventsPointer + 4)%number_of_upcoming_events;
 
-	// get player and missile proposed pixels
-	uint8_t playerPixels[2] = {0, 0}, missilePixels[2] = {0, 0};
-	for(int c = 0; c < 2; c++)
+	_objectCounterPointer = (_objectCounterPointer + 1)%number_of_recorded_counters;
+	ObjectCounter *oneClockAgo = _objectCounter[(_objectCounterPointer - 1 + number_of_recorded_counters)%number_of_recorded_counters];
+	ObjectCounter *twoClocksAgo = _objectCounter[(_objectCounterPointer - 2 + number_of_recorded_counters)%number_of_recorded_counters];
+	ObjectCounter *now = _objectCounter[_objectCounterPointer];
+
+	// grab the background now, for application in four clocks
+	if(mask & (1 << 5) && !(_horizontalTimer&3))
 	{
-		const uint8_t repeatMask = _playerAndMissileSize[c]&7;
-		if(_playerGraphics[c]) {
-			// figure out player colour
-			int flipMask = (_playerReflection[c]&0x8) ? 0 : 7;
-
-			int relativeTimer = _objectCounter[c] - 5;
-			switch (repeatMask)
-			{
-				case 0: break;
-				default:
-					if(repeatMask&4 && relativeTimer >= 64) relativeTimer -= 64;
-					else if(repeatMask&2 && relativeTimer >= 32) relativeTimer -= 32;
-					else if(repeatMask&1 && relativeTimer >= 16) relativeTimer -= 16;
-				break;
-				case 5:
-					relativeTimer >>= 1;
-				break;
-				case 7:
-					relativeTimer >>= 2;
-				break;
-			}
-
-			if(relativeTimer >= 0 && relativeTimer < 8)
-				playerPixels[c] = (_playerGraphics[c] >> (relativeTimer ^ flipMask)) &1;
-		}
-
-		// figure out missile colour
-		if((_missileGraphicsEnable[c]&2) && !(_missileGraphicsReset[c]&2)) {
-			int missileIndex = _objectCounter[2+c] - 4;
-			switch (repeatMask)
-			{
-				case 0: break;
-				default:
-					if(repeatMask&4 && missileIndex >= 64) missileIndex -= 64;
-					else if(repeatMask&2 && missileIndex >= 32) missileIndex -= 32;
-					else if(repeatMask&1 && missileIndex >= 16) missileIndex -= 16;
-				break;
-				case 5:
-					missileIndex >>= 1;
-				break;
-				case 7:
-					missileIndex >>= 2;
-				break;
-			}
-			int missileSize = 1 << ((_playerAndMissileSize[c] >> 4)&3);
-			missilePixels[c] = (missileIndex >= 0 && missileIndex < missileSize) ? 1 : 0;
-		}
+		unsigned int offset = 4 + _horizontalTimer - (horizontalTimerPeriod - 160);
+		_upcomingEvents[upcomingPointerPlus4].updates |= Event::Action::Playfield;
+		_upcomingEvents[upcomingPointerPlus4].playfieldPixel = _playfield[(offset >> 2)%40];
 	}
 
-	// get the ball proposed colour
+	if(mask & (1 << 4))
+	{
+		// the ball becomes visible whenever it hits zero, regardless of whether its status
+		// is the result of a counter rollover or a programmatic reset, and there's a four
+		// clock delay on that triggering the start signal
+		now[4].count = (oneClockAgo[4].count + 1)%160;
+		now[4].pixel = oneClockAgo[4].pixel + 1;
+		if(!now[4].count) now[4].pixel = 0;
+	}
+	else
+	{
+		now[4] = oneClockAgo[4];
+	}
+
+	// check for player and missle triggers
+	for(int c = 0; c < 4; c++)
+	{
+		if(mask & (1 << c))
+		{
+			// update the count
+			now[c].count = (oneClockAgo[c].count + 1)%160;
+
+			uint8_t repeatMask = _playerAndMissileSize[c&1] & 7;
+			ObjectCounter *rollover;
+			ObjectCounter *equality;
+
+			if(c < 2)
+			{
+				// update the pixel
+				now[c].broad_pixel = oneClockAgo[c].broad_pixel + 1;
+				switch(repeatMask)
+				{
+					default:	now[c].pixel = oneClockAgo[c].pixel + 1;	break;
+					case 5:		now[c].pixel = oneClockAgo[c].pixel + (now[c].broad_pixel&1);	break;
+					case 7:		now[c].pixel = oneClockAgo[c].pixel + (((now[c].broad_pixel | (now[c].broad_pixel >> 1))^1)&1);	break;
+				}
+
+				// check for a rollover six clocks ago or equality five clocks ago
+				rollover = twoClocksAgo;
+				equality = oneClockAgo;
+			}
+			else
+			{
+				// update the pixel
+				now[c].pixel = oneClockAgo[c].pixel + 1;
+
+				// check for a rollover five clocks ago or equality four clocks ago
+				rollover = oneClockAgo;
+				equality = now;
+			}
+
+			if(
+				(rollover[c].count == 159) ||
+				(_hasSecondCopy[c&1] && equality[c].count == 16) ||
+				(_hasThirdCopy[c&1] && equality[c].count == 32) ||
+				(_hasFourthCopy[c&1] && equality[c].count == 64)
+			)
+			{
+				now[c].pixel = 0;
+				now[c].broad_pixel = 0;
+			}
+		}
+		else
+		{
+			now[c] = oneClockAgo[c];
+		}
+	}
+}
+
+uint8_t Machine::get_output_pixel()
+{
+	ObjectCounter *now = _objectCounter[_objectCounterPointer];
+
+	// get the playfield pixel
+	unsigned int offset = _horizontalTimer - (horizontalTimerPeriod - 160);
+	uint8_t playfieldColour = ((_playfieldControl&6) == 2) ? _playerColour[offset / 80] : _playfieldColour;
+
+	// ball pixel
 	uint8_t ballPixel = 0;
-	if(_ballGraphicsEnable&2) {
-		int ballIndex = _objectCounter[4] - 4;
-		int ballSize = 1 << ((_playfieldControl >> 4)&3);
-		ballPixel = (ballIndex >= 0 && ballIndex < ballSize) ? 1 : 0;
+	if(now[4].pixel < _ballSize) {
+		ballPixel = _ballGraphicsEnable[_ballGraphicsSelector];
+	}
+
+	// determine the player and missile pixels
+	uint8_t playerPixels[2] = { 0, 0 };
+	uint8_t missilePixels[2] = { 0, 0 };
+	for(int c = 0; c < 2; c++)
+	{
+		if(_playerGraphics[c] && now[c].pixel < 8) {
+			playerPixels[c] = (_playerGraphics[_playerGraphicsSelector[c]][c] >> (now[c].pixel ^ _playerReflectionMask[c])) & 1;
+		}
+
+		if(!_missileGraphicsReset[c] && now[c+2].pixel < _missileSize[c]) {
+			missilePixels[c] = _missileGraphicsEnable[c];
+		}
 	}
 
 	// accumulate collisions
-	if(playerPixels[0] | playerPixels[1]) {
-		_collisions[0] |= ((missilePixels[0] & playerPixels[1]) << 7)	| ((missilePixels[0] & playerPixels[0]) << 6);
-		_collisions[1] |= ((missilePixels[1] & playerPixels[0]) << 7)	| ((missilePixels[1] & playerPixels[1]) << 6);
-
-		_collisions[2] |= ((playfieldPixel & playerPixels[0]) << 7)		| ((ballPixel & playerPixels[0]) << 6);
-		_collisions[3] |= ((playfieldPixel & playerPixels[1]) << 7)		| ((ballPixel & playerPixels[1]) << 6);
-
-		_collisions[7] |= ((playerPixels[0] & playerPixels[1]) << 7);
-	}
-
-	if(playfieldPixel | ballPixel) {
-		_collisions[4] |= ((playfieldPixel & missilePixels[0]) << 7)	| ((ballPixel & missilePixels[0]) << 6);
-		_collisions[5] |= ((playfieldPixel & missilePixels[1]) << 7)	| ((ballPixel & missilePixels[1]) << 6);
-
-		_collisions[6] |= ((playfieldPixel & ballPixel) << 7);
-	}
-
-	if(missilePixels[0] & missilePixels[1])
-		_collisions[7] |= (1 << 6);
+	int pixel_mask = playerPixels[0] | (playerPixels[1] << 1) | (missilePixels[0] << 2) | (missilePixels[1] << 3) | (ballPixel << 4) | (_playfieldOutput << 5);
+	_collisions[0] |= _reportedCollisions[pixel_mask][0];
+	_collisions[1] |= _reportedCollisions[pixel_mask][1];
+	_collisions[2] |= _reportedCollisions[pixel_mask][2];
+	_collisions[3] |= _reportedCollisions[pixel_mask][3];
+	_collisions[4] |= _reportedCollisions[pixel_mask][4];
+	_collisions[5] |= _reportedCollisions[pixel_mask][5];
+	_collisions[6] |= _reportedCollisions[pixel_mask][6];
+	_collisions[7] |= _reportedCollisions[pixel_mask][7];
 
 	// apply appropriate priority to pick a colour
-	playfieldPixel |= ballPixel;
+	uint8_t playfieldPixel = _playfieldOutput | ballPixel;
 	uint8_t outputColour = playfieldPixel ? playfieldColour : _backgroundColour;
 
 	if(!(_playfieldControl&0x04) || !playfieldPixel) {
@@ -172,73 +242,131 @@ void Machine::get_output_pixel(uint8_t *pixel, int offset)
 		if(playerPixels[0] || missilePixels[0]) outputColour = _playerColour[0];
 	}
 
-	// store colour
-//	static int lc;
-//	if(_vSyncEnabled) lc = 0; else lc += (offset == 159) ? 1 : 0;
-//	*pixel = (uint8_t)(((offset  / 10) << 4) | (((lc >> 4)&7) << 1));
-	*pixel = outputColour;
+	// return colour
+	return outputColour;
 }
 
-// in imputing the knowledge that all we're dealing with is the rollover from 159 to 0,
-// this is faster than the straightforward +1)%160 per profiling
-#define increment_object_counter(c) _objectCounter[c] = (_objectCounter[c]+1)&~((158-_objectCounter[c]) >> 8)
+void Machine::setup_reported_collisions()
+{
+	for(int c = 0; c < 64; c++)
+	{
+		memset(_reportedCollisions[c], 0, 8);
+
+		int playerPixels[2] = { c&1, (c >> 1)&1 };
+		int missilePixels[2] = { (c >> 2)&1, (c >> 3)&1 };
+		int ballPixel = (c >> 4)&1;
+		int playfieldPixel = (c >> 5)&1;
+
+		if(playerPixels[0] | playerPixels[1]) {
+			_reportedCollisions[c][0] |= ((missilePixels[0] & playerPixels[1]) << 7)	| ((missilePixels[0] & playerPixels[0]) << 6);
+			_reportedCollisions[c][1] |= ((missilePixels[1] & playerPixels[0]) << 7)	| ((missilePixels[1] & playerPixels[1]) << 6);
+
+			_reportedCollisions[c][2] |= ((playfieldPixel & playerPixels[0]) << 7)	| ((ballPixel & playerPixels[0]) << 6);
+			_reportedCollisions[c][3] |= ((playfieldPixel & playerPixels[1]) << 7)	| ((ballPixel & playerPixels[1]) << 6);
+
+			_reportedCollisions[c][7] |= ((playerPixels[0] & playerPixels[1]) << 7);
+		}
+
+		if(playfieldPixel | ballPixel) {
+			_reportedCollisions[c][4] |= ((playfieldPixel & missilePixels[0]) << 7)	| ((ballPixel & missilePixels[0]) << 6);
+			_reportedCollisions[c][5] |= ((playfieldPixel & missilePixels[1]) << 7)	| ((ballPixel & missilePixels[1]) << 6);
+
+			_reportedCollisions[c][6] |= ((playfieldPixel & ballPixel) << 7);
+		}
+
+		if(missilePixels[0] & missilePixels[1])
+			_reportedCollisions[c][7] |= (1 << 6);
+	}
+}
 
 void Machine::output_pixels(unsigned int count)
 {
-	const int32_t start_of_sync = 214;
-	const int32_t end_of_sync = 198;
-	const int32_t end_of_colour_burst = 188;
-
 	while(count--)
 	{
-		OutputState state;
+		if(_upcomingEvents[_upcomingEventsPointer].updates)
+		{
+			// apply any queued changes and flush the record
+			if(_upcomingEvents[_upcomingEventsPointer].updates & Event::Action::HMoveSetup)
+			{
+				// schedule an extended left border
+				_stateByTime = _stateByExtendTime[1];
 
-		// update hmove
-		if(!(_horizontalTimer&3)) {
+				// clear any ongoing moves
+				if(_hMoveFlags)
+				{
+					for(int c = 0; c < number_of_upcoming_events; c++)
+					{
+						_upcomingEvents[c].updates &= ~(Event::Action::HMoveCompare | Event::Action::HMoveDecrement);
+					}
+				}
 
-			if(_hMoveFlags) {
-				const uint8_t counterValue = _hMoveCounter ^ 0x7;
-				for(int c = 0; c < 5; c++) {
-					if(counterValue == (_objectMotion[c] >> 4)) _hMoveFlags &= ~(1 << c);
-					if(_hMoveFlags&(1 << c)) increment_object_counter(c);
+				// schedule new moves
+				_hMoveFlags = 0x1f;
+				_hMoveCounter = 15;
+
+				// follow-through into a compare immediately
+				_upcomingEvents[_upcomingEventsPointer].updates |= Event::Action::HMoveCompare;
+			}
+
+			if(_upcomingEvents[_upcomingEventsPointer].updates & Event::Action::HMoveCompare)
+			{
+				for(int c = 0; c < 5; c++)
+				{
+					if(((_objectMotion[c] >> 4)^_hMoveCounter) == 7)
+					{
+						_hMoveFlags &= ~(1 << c);
+					}
+				}
+				if(_hMoveFlags)
+				{
+					if(_hMoveCounter) _hMoveCounter--;
+					_upcomingEvents[(_upcomingEventsPointer+4)%number_of_upcoming_events].updates |= Event::Action::HMoveCompare;
+					_upcomingEvents[(_upcomingEventsPointer+2)%number_of_upcoming_events].updates |= Event::Action::HMoveDecrement;
 				}
 			}
 
-			if(_hMoveIsCounting) {
-				_hMoveIsCounting = !!_hMoveCounter;
-				_hMoveCounter = (_hMoveCounter-1)&0xf;
+			if(_upcomingEvents[_upcomingEventsPointer].updates & Event::Action::HMoveDecrement)
+			{
+				update_timers(_hMoveFlags);
 			}
+
+			if(_upcomingEvents[_upcomingEventsPointer].updates & Event::Action::ResetCounter)
+			{
+				_objectCounter[_objectCounterPointer][_upcomingEvents[_upcomingEventsPointer].counter].count = 0;
+			}
+
+			// zero out current update event
+			_upcomingEvents[_upcomingEventsPointer].updates = 0;
 		}
 
+		//  progress to next event
+		_upcomingEventsPointer = (_upcomingEventsPointer + 1)%number_of_upcoming_events;
 
-		// blank is decoded as 68 counts; sync and colour burst as 16 counts
+		// determine which output state is currently active
+		OutputState primary_state = _stateByTime[_horizontalTimer >> 2];
+		OutputState effective_state = primary_state;
 
-		// 4 blank
-		// 4 sync
-		// 9 'blank'; colour burst after 4
-		// 40 pixels
+		// update pixel timers
+		if(primary_state == OutputState::Pixel) update_timers(~0);
 
-		// it'll be about 43 cycles from start of hsync to start of visible frame, so...
-		// guesses, until I can find information: 26 cycles blank, 16 sync, 40 blank, 160 pixels
-		if(_horizontalTimer < (_vBlankExtend ? 152 : 160)) {
-			if(_vBlankEnabled) {
-				state = OutputState::Blank;
-			} else {
-				state = OutputState::Pixel;
-			}
+		// update the background chain
+		if(_horizontalTimer >= 64 && _horizontalTimer <= 160+64 && !(_horizontalTimer&3))
+		{
+			_playfieldOutput = _nextPlayfieldOutput;
+			_nextPlayfieldOutput = _playfield[(_horizontalTimer - 64) >> 2];
 		}
-		else if(_horizontalTimer < end_of_colour_burst) state = OutputState::Blank;
-		else if(_horizontalTimer < end_of_sync) state = OutputState::ColourBurst;
-		else if(_horizontalTimer < start_of_sync) state = OutputState::Sync;
-		else state = OutputState::Blank;
 
-		// logic: if vsync is enabled, output the opposite of the automatic hsync output
+		// if vsync is enabled, output the opposite of the automatic hsync output;
+		// also	honour the vertical blank flag
 		if(_vSyncEnabled) {
-			state = (state = OutputState::Sync) ? OutputState::Blank : OutputState::Sync;
+			effective_state = (effective_state = OutputState::Sync) ? OutputState::Blank : OutputState::Sync;
+		} else if(_vBlankEnabled && effective_state == OutputState::Pixel) {
+			effective_state = OutputState::Blank;
 		}
 
+		// decide what that means needs to be communicated to the CRT
 		_lastOutputStateDuration++;
-		if(state != _lastOutputState) {
+		if(effective_state != _lastOutputState) {
 			switch(_lastOutputState) {
 				case OutputState::Blank:		_crt->output_blank(_lastOutputStateDuration);				break;
 				case OutputState::Sync:			_crt->output_sync(_lastOutputStateDuration);				break;
@@ -246,35 +374,34 @@ void Machine::output_pixels(unsigned int count)
 				case OutputState::Pixel:		_crt->output_data(_lastOutputStateDuration,	1);				break;
 			}
 			_lastOutputStateDuration = 0;
-			_lastOutputState = state;
+			_lastOutputState = effective_state;
 
-			if(state == OutputState::Pixel) {
+			if(effective_state == OutputState::Pixel) {
 				_outputBuffer = _crt->allocate_write_area(160);
 			} else {
 				_outputBuffer = nullptr;
 			}
 		}
 
-		if(_horizontalTimer < (_vBlankExtend ? 152 : 160)) {
-			uint8_t throwaway_pixel;
-			get_output_pixel(_outputBuffer ? &_outputBuffer[_lastOutputStateDuration] : &throwaway_pixel, 159 - _horizontalTimer);
-
-			// increment all graphics counters
-			increment_object_counter(0);
-			increment_object_counter(1);
-			increment_object_counter(2);
-			increment_object_counter(3);
-			increment_object_counter(4);
+		// decide on a pixel colour if that's what's happening
+		if(effective_state == OutputState::Pixel)
+		{
+			uint8_t colour = get_output_pixel();
+			if(_outputBuffer)
+			{
+				*_outputBuffer = colour;
+				_outputBuffer++;
+			}
 		}
 
-		// assumption here: signed shifts right; otherwise it's just
-		// an attempt to avoid both the % operator and a conditional
-		_horizontalTimer--;
-		const int32_t sign_extension = _horizontalTimer >> 31;
-		_horizontalTimer = (_horizontalTimer&~sign_extension) | (sign_extension&horizontalTimerReload);
-
+		// advance horizontal timer, perform reset actions if desired
+		_horizontalTimer = (_horizontalTimer + 1) % horizontalTimerPeriod;
 		if(!_horizontalTimer)
-			_vBlankExtend = false;
+		{
+			// switch back to a normal length left border
+			_stateByTime = _stateByExtendTime[0];
+			set_ready_line(false);
+		}
 	}
 }
 
@@ -283,26 +410,19 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 	set_reset_line(false);
 
 	uint8_t returnValue = 0xff;
-	unsigned int cycles_run_for = 1;
-	const int32_t ready_line_disable_time = 227;//horizontalTimerReload;
+	unsigned int cycles_run_for = 3;
 
+	// this occurs as a feedback loop — the 2600 requests ready, then performs the cycles_run_for
+	// leap to the end of ready only once ready is signalled — because on a 6502 ready doesn't take
+	// effect until the next read; therefore it isn't safe to assume that signalling ready immediately
+	// skips to the end of the line.
 	if(operation == CPU6502::BusOperation::Ready) {
-		unsigned int distance_to_end_of_ready = (_horizontalTimer - ready_line_disable_time + horizontalTimerReload + 1)%(horizontalTimerReload + 1);
-		cycles_run_for = distance_to_end_of_ready / 3;
-		output_pixels(distance_to_end_of_ready);
-	} else {
-		output_pixels(3);
+		unsigned int distance_to_end_of_ready = horizontalTimerPeriod - _horizontalTimer;
+		cycles_run_for = distance_to_end_of_ready;
 	}
 
-	if(_hMoveWillCount) {
-		_hMoveCounter = 0x0f;
-		_hMoveFlags = 0x1f;
-		_hMoveIsCounting = true;
-		_hMoveWillCount = false;
-	}
-
-	if(_horizontalTimer == ready_line_disable_time)
-		set_ready_line(false);
+	output_pixels(cycles_run_for);
+	_cycles_since_speaker_update += cycles_run_for;
 
 	if(operation != CPU6502::BusOperation::Ready) {
 
@@ -378,14 +498,26 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 					case 0x01:	_vBlankEnabled = !!(*value & 0x02);	break;
 
 					case 0x02:
-						set_ready_line(true);
+						if(_horizontalTimer) set_ready_line(true);
 					break;
 					case 0x03:
-						_horizontalTimer = 0;
+						// Reset is delayed by four cycles.
+						_horizontalTimer = horizontalTimerPeriod - 4;
+
+						// TODO: audio will now be out of synchronisation — fix
 					break;
 
 					case 0x04:
-					case 0x05: _playerAndMissileSize[decodedAddress - 0x04] = *value;	break;
+					case 0x05: {
+						int entry = decodedAddress - 0x04;
+						_playerAndMissileSize[entry] = *value;
+						_missileSize[entry] = 1 << ((*value >> 4)&3);
+
+						uint8_t repeatMask = (*value)&7;
+						_hasSecondCopy[entry] = (repeatMask == 1) || (repeatMask == 3);
+						_hasThirdCopy[entry] = (repeatMask == 2) || (repeatMask == 3) || (repeatMask == 6);
+						_hasFourthCopy[entry] = (repeatMask == 4) || (repeatMask == 6);
+					} break;
 
 					case 0x06:
 					case 0x07: _playerColour[decodedAddress - 0x06] = *value;	break;
@@ -395,6 +527,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 					case 0x0a: {
 						uint8_t old_playfield_control = _playfieldControl;
 						_playfieldControl = *value;
+						_ballSize = 1 << ((_playfieldControl >> 4)&3);
 
 						// did the mirroring bit change?
 						if((_playfieldControl^old_playfield_control)&1) {
@@ -406,7 +539,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 						}
 					} break;
 					case 0x0b:
-					case 0x0c: _playerReflection[decodedAddress - 0x0b] = *value;	break;
+					case 0x0c: _playerReflectionMask[decodedAddress - 0x0b] = (*value)&8 ? 0 : 7;	break;
 
 					case 0x0d:
 						_playfield[0] = ((*value) >> 4)&1;
@@ -454,23 +587,40 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 					break;
 
 					case 0x10:	case 0x11:	case 0x12:	case 0x13:
-					case 0x14: _objectCounter[decodedAddress - 0x10] = 0;		break;
+					case 0x14:
+						_upcomingEvents[(_upcomingEventsPointer + 4)%number_of_upcoming_events].updates |= Event::Action::ResetCounter;
+						_upcomingEvents[(_upcomingEventsPointer + 4)%number_of_upcoming_events].counter = decodedAddress - 0x10;
+					break;
+
+					case 0x15: case 0x16:
+						update_audio();
+						_speaker.set_control(decodedAddress - 0x15, *value);
+					break;
+
+					case 0x17: case 0x18:
+						update_audio();
+						_speaker.set_divider(decodedAddress - 0x17, *value);
+					break;
+
+					case 0x19: case 0x1a:
+						update_audio();
+						_speaker.set_volume(decodedAddress - 0x19, *value);
+					break;
 
 					case 0x1c:
-						_ballGraphicsEnable = _ballGraphicsEnableLatch;
+						_ballGraphicsEnable[1] = _ballGraphicsEnable[0];
 					case 0x1b: {
 						int index = decodedAddress - 0x1b;
-						_playerGraphicsLatch[index] = *value;
-						if(!(_playerGraphicsLatchEnable[index]&1))
-							_playerGraphics[index] = _playerGraphicsLatch[index];
-						_playerGraphics[index^1] = _playerGraphicsLatch[index^1];
+						_playerGraphics[0][index] = *value;
+						_playerGraphics[1][index^1] = _playerGraphics[0][index^1];
 					} break;
-					case 0x1d: _missileGraphicsEnable[0] = *value;	break;
-					case 0x1e: _missileGraphicsEnable[1] = *value;	break;
+					case 0x1d:
+					case 0x1e:
+						_missileGraphicsEnable[decodedAddress - 0x1d] = ((*value) >> 1)&1;
+//						printf("e:%02x <- %c\n", decodedAddress - 0x1d, ((*value)&1) ? 'E' : '-');
+					break;
 					case 0x1f:
-						_ballGraphicsEnableLatch = *value;
-						if(!(_ballGraphicsEnableDelay&1))
-							_ballGraphicsEnable = _ballGraphicsEnableLatch;
+						_ballGraphicsEnable[0] = ((*value) >> 1)&1;
 					break;
 
 					case 0x20:
@@ -481,21 +631,42 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 						_objectMotion[decodedAddress - 0x20] = *value;
 					break;
 
-					case 0x25: _playerGraphicsLatchEnable[0] = *value;	break;
-					case 0x26: _playerGraphicsLatchEnable[1] = *value;	break;
-					case 0x27: _ballGraphicsEnableDelay = *value;		break;
+					case 0x25: _playerGraphicsSelector[0]	= (*value)&1;	break;
+					case 0x26: _playerGraphicsSelector[1]	= (*value)&1;	break;
+					case 0x27: _ballGraphicsSelector		= (*value)&1;	break;
 
 					case 0x28:
 					case 0x29:
-						if(!(*value&0x02) && _missileGraphicsReset[decodedAddress - 0x28]&0x02)
-							_objectCounter[decodedAddress - 0x26] = _objectCounter[decodedAddress - 0x28];  // TODO: +3 for normal, +6 for double, +10 for quad
-						_missileGraphicsReset[decodedAddress - 0x28] = *value;
+					{
+						// TODO: this should properly mean setting a flag and propagating later, I think?
+						int index = decodedAddress - 0x28;
+						if(!(*value&0x02) && _missileGraphicsReset[index])
+						{
+							_objectCounter[_objectCounterPointer][index + 2].count = _objectCounter[_objectCounterPointer][index].count;
+
+							uint8_t repeatMask = _playerAndMissileSize[index] & 7;
+							int extra_offset;
+							switch(repeatMask)
+							{
+								default:	extra_offset = 3;	break;
+								case 5:		extra_offset = 6;	break;
+								case 7:		extra_offset = 10;	break;
+							}
+
+							_objectCounter[_objectCounterPointer][index + 2].count = (_objectCounter[_objectCounterPointer][index + 2].count + extra_offset)%160;
+						}
+						_missileGraphicsReset[index] = !!((*value) & 0x02);
+//						printf("r:%02x <- %c\n", decodedAddress - 0x28, ((*value)&2) ? 'R' : '-');
+					}
 					break;
 
-					case 0x2a:
-						_vBlankExtend = true;
-						_hMoveWillCount = true;
-					break;
+					case 0x2a: {
+						// justification for +5: "we need to wait at least 71 [clocks] before the HMOVE operation is complete";
+						// which will take 16*4 + 2 = 66 cycles from the first compare, implying the first compare must be
+						// in five cycles from now
+//						int start_pause = ((_horizontalTimer + 3)&3) + 4;
+						_upcomingEvents[(_upcomingEventsPointer + 5)%number_of_upcoming_events].updates |= Event::Action::HMoveSetup;
+					} break;
 					case 0x2b:
 						_objectMotion[0] =
 						_objectMotion[1] =
@@ -525,8 +696,10 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 					case 0x01:
 					case 0x03:
 						// TODO: port DDR
+						printf("!!!DDR!!!");
 					break;
 					case 0x04:
+					case 0x06:
 						returnValue &= _piaTimerValue >> _piaTimerShift;
 
 						if(_writtenPiaTimerShift != _piaTimerShift) {
@@ -535,8 +708,9 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 						}
 					break;
 					case 0x05:
+					case 0x07:
 						returnValue &= _piaTimerStatus;
-						_piaTimerStatus &= ~0x40;
+						_piaTimerStatus &= ~0x80;
 					break;
 				}
 			} else {
@@ -546,9 +720,9 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 					case 0x05:
 					case 0x06:
 					case 0x07:
-						_writtenPiaTimerShift = _piaTimerShift = (decodedAddress - 0x04) * 3 + (decodedAddress / 0x07);
-						_piaTimerValue = (unsigned int)(*value << _piaTimerShift);
-						_piaTimerStatus &= ~0xc0;
+						_writtenPiaTimerShift = _piaTimerShift = (decodedAddress - 0x04) * 3 + (decodedAddress / 0x07);	// i.e. 0, 3, 6, 10
+						_piaTimerValue = (unsigned int)(*value) << _piaTimerShift;
+						_piaTimerStatus &= ~0x40;
 					break;
 				}
 			}
@@ -559,15 +733,26 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 		}
 	}
 
-	if(_piaTimerValue >= cycles_run_for) {
-		_piaTimerValue -= cycles_run_for;
+	if(_piaTimerValue >= cycles_run_for / 3) {
+		_piaTimerValue -= cycles_run_for / 3;
 	} else {
-		_piaTimerValue += 0xff - cycles_run_for;
+		_piaTimerValue = 0x100 + ((_piaTimerValue - (cycles_run_for / 3)) >> _piaTimerShift);
 		_piaTimerShift = 0;
 		_piaTimerStatus |= 0xc0;
 	}
 
-	return cycles_run_for;
+//	static unsigned int total_cycles = 0;
+//	total_cycles += cycles_run_for / 3;
+//	static time_t logged_time = 0;
+//	time_t time_now = time(nullptr);
+//	if(time_now - logged_time > 0)
+//	{
+//		printf("[c] %ld : %d\n", time_now - logged_time, total_cycles);
+//		total_cycles = 0;
+//		logged_time = time_now;
+//	}
+
+	return cycles_run_for / 3;
 }
 
 void Machine::set_digital_input(Atari2600DigitalInput input, bool state)
@@ -615,3 +800,159 @@ void Machine::set_rom(size_t length, const uint8_t *data)
 	_romPages[2] = &_rom[2048 & romMask];
 	_romPages[3] = &_rom[3072 & romMask];
 }
+
+#pragma mark - Audio
+
+void Machine::update_audio()
+{
+	unsigned int audio_cycles = _cycles_since_speaker_update / 114;
+
+//	static unsigned int total_cycles = 0;
+//	total_cycles += audio_cycles;
+//	static time_t logged_time = 0;
+//	time_t time_now = time(nullptr);
+//	if(time_now - logged_time > 0)
+//	{
+//		printf("[s] %ld : %d\n", time_now - logged_time, total_cycles);
+//		total_cycles = 0;
+//		logged_time = time_now;
+//	}
+
+	_speaker.run_for_cycles(audio_cycles);
+	_cycles_since_speaker_update %= 114;
+}
+
+void Machine::synchronise()
+{
+	update_audio();
+}
+
+Atari2600::Speaker::Speaker()
+{
+	_poly4_counter[0] = _poly4_counter[1] = 0x00f;
+	_poly5_counter[0] = _poly5_counter[1] = 0x01f;
+	_poly9_counter[0] = _poly9_counter[1] = 0x1ff;
+}
+
+Atari2600::Speaker::~Speaker()
+{
+}
+
+void Atari2600::Speaker::set_volume(int channel, uint8_t volume)
+{
+	_volume[channel] = volume & 0xf;
+}
+
+void Atari2600::Speaker::set_divider(int channel, uint8_t divider)
+{
+	_divider[channel] = divider & 0x1f;
+	_divider_counter[channel] = 0;
+}
+
+void Atari2600::Speaker::set_control(int channel, uint8_t control)
+{
+	_control[channel] = control & 0xf;
+}
+
+#define advance_poly4(c) _poly4_counter[channel] = (_poly4_counter[channel] >> 1) | (((_poly4_counter[channel] << 3) ^ (_poly4_counter[channel] << 2))&0x008)
+#define advance_poly5(c) _poly5_counter[channel] = (_poly5_counter[channel] >> 1) | (((_poly5_counter[channel] << 4) ^ (_poly5_counter[channel] << 2))&0x010)
+#define advance_poly9(c) _poly9_counter[channel] = (_poly9_counter[channel] >> 1) | (((_poly9_counter[channel] << 4) ^ (_poly9_counter[channel] << 8))&0x100)
+
+
+void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *target)
+{
+	for(unsigned int c = 0; c < number_of_samples; c++)
+	{
+		target[c] = 0;
+		for(int channel = 0; channel < 2; channel++)
+		{
+			_divider_counter[channel] ++;
+			int level = 0;
+			switch(_control[channel])
+			{
+				case 0x0: case 0xb:	// constant 1
+					level = 1;
+				break;
+
+				case 0x4: case 0x5:	// div2 tone
+					level = (_divider_counter[channel] / (_divider[channel]+1))&1;
+				break;
+
+				case 0xc: case 0xd:	// div6 tone
+					level = (_divider_counter[channel] / ((_divider[channel]+1)*3))&1;
+				break;
+
+				case 0x6: case 0xa:	// div31 tone
+					level = (_divider_counter[channel] / (_divider[channel]+1))%30 <= 18;
+				break;
+
+				case 0xe:			// div93 tone
+					level = (_divider_counter[channel] / ((_divider[channel]+1)*3))%30 <= 18;
+				break;
+
+				case 0x1:			// 4-bit poly
+					level = _poly4_counter[channel]&1;
+					if(_divider_counter[channel] == _divider[channel]+1)
+					{
+						_divider_counter[channel] = 0;
+						advance_poly4(channel);
+					}
+				break;
+
+				case 0x2:			// 4-bit poly div31
+					level = _poly4_counter[channel]&1;
+					if(_divider_counter[channel]%(30*(_divider[channel]+1)) == 18)
+					{
+						advance_poly4(channel);
+					}
+				break;
+
+				case 0x3:			// 5/4-bit poly
+					level = _output_state[channel];
+					if(_divider_counter[channel] == _divider[channel]+1)
+					{
+						if(_poly5_counter[channel]&1)
+						{
+							_output_state[channel] = _poly4_counter[channel]&1;
+							advance_poly4(channel);
+						}
+						advance_poly5(channel);
+					}
+				break;
+
+				case 0x7: case 0x9:	// 5-bit poly
+					level = _poly5_counter[channel]&1;
+					if(_divider_counter[channel] == _divider[channel]+1)
+					{
+						_divider_counter[channel] = 0;
+						advance_poly5(channel);
+					}
+				break;
+
+				case 0xf:			// 5-bit poly div6
+					level = _poly5_counter[channel]&1;
+					if(_divider_counter[channel] == (_divider[channel]+1)*3)
+					{
+						_divider_counter[channel] = 0;
+						advance_poly5(channel);
+					}
+				break;
+
+				case 0x8:			// 9-bit poly
+					level = _poly9_counter[channel]&1;
+					if(_divider_counter[channel] == _divider[channel]+1)
+					{
+						_divider_counter[channel] = 0;
+						advance_poly9(channel);
+					}
+				break;
+			}
+
+			target[c] += _volume[channel] * 1024 * level;
+		}
+	}
+}
+
+void Atari2600::Speaker::skip_samples(unsigned int number_of_samples)
+{
+}
diff --git a/Machines/Atari2600/Atari2600.hpp b/Machines/Atari2600/Atari2600.hpp
index 12b0c4d9e..656cc844d 100644
--- a/Machines/Atari2600/Atari2600.hpp
+++ b/Machines/Atari2600/Atari2600.hpp
@@ -10,28 +10,64 @@
 #define Atari2600_cpp
 
 #include "../../Processors/6502/CPU6502.hpp"
-#include "../../Outputs/CRT/CRT.hpp"
+#include "../CRTMachine.hpp"
 #include <stdint.h>
 #include "Atari2600Inputs.h"
 
 namespace Atari2600 {
 
-class Machine: public CPU6502::Processor<Machine> {
+const unsigned int number_of_upcoming_events = 6;
+const unsigned int number_of_recorded_counters = 7;
+
+class Speaker: public ::Outputs::Filter<Speaker> {
+	public:
+		Speaker();
+		~Speaker();
+
+		void set_volume(int channel, uint8_t volume);
+		void set_divider(int channel, uint8_t divider);
+		void set_control(int channel, uint8_t control);
+
+		void get_samples(unsigned int number_of_samples, int16_t *target);
+		void skip_samples(unsigned int number_of_samples);
+
+	private:
+		uint8_t _volume[2];
+		uint8_t _divider[2];
+		uint8_t _control[2];
+
+		int _poly4_counter[2];
+		int _poly5_counter[2];
+		int _poly9_counter[2];
+		int _output_state[2];
+
+		int _divider_counter[2];
+
+		int _pattern_periods[16];
+		int _patterns[16][512];
+};
+
+class Machine: public CPU6502::Processor<Machine>, public CRTMachine::Machine {
 
 	public:
 		Machine();
 		~Machine();
 
-		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
-
 		void set_rom(size_t length, const uint8_t *data);
 		void switch_region();
 
 		void set_digital_input(Atari2600DigitalInput input, bool state);
 
-		Outputs::CRT::CRT *get_crt() { return _crt; }
-		void setup_output(float aspect_ratio);
-		void close_output();
+		// to satisfy CPU6502::Processor
+		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
+		void synchronise();
+
+		// to satisfy CRTMachine::Machine
+		virtual void setup_output(float aspect_ratio);
+		virtual void close_output();
+		virtual Outputs::CRT::CRT *get_crt() { return _crt; }
+		virtual Outputs::Speaker *get_speaker() { return &_speaker; }
+		virtual void run_for_cycles(int number_of_cycles) { CPU6502::Processor<Machine>::run_for_cycles(number_of_cycles); }
 
 	private:
 		uint8_t *_rom, *_romPages[4], _ram[128];
@@ -46,32 +82,81 @@ class Machine: public CPU6502::Processor<Machine> {
 		uint8_t _playfieldControl;
 		uint8_t _playfieldColour;
 		uint8_t _backgroundColour;
-		uint8_t _playfield[40];
+		uint8_t _playfield[41];
+
+		// ... and derivatives
+		int _ballSize, _missileSize[2];
+
+		// delayed clock events
+		enum OutputState {
+			Sync,
+			Blank,
+			ColourBurst,
+			Pixel
+		};
+
+		struct Event {
+			enum Action {
+				Playfield			= 1 << 0,
+				ResetCounter		= 1 << 1,
+
+				HMoveSetup			= 1 << 2,
+				HMoveCompare		= 1 << 3,
+				HMoveDecrement		= 1 << 4,
+			};
+			int updates;
+
+			OutputState state;
+			uint8_t playfieldPixel;
+			int counter;
+
+			Event() : updates(0), playfieldPixel(0) {}
+		} _upcomingEvents[number_of_upcoming_events];
+		unsigned int _upcomingEventsPointer;
+
+		// object counters
+		struct ObjectCounter {
+			int count;			// the counter value, multiplied by four, counting phase
+			int pixel;			// for non-sprite objects, a count of cycles since the last counter reset; for sprite objects a count of pixels so far elapsed
+			int broad_pixel;	// for sprite objects, a count of cycles since the last counter reset; otherwise unused
+
+			ObjectCounter() : count(0), pixel(0), broad_pixel(0) {}
+		} _objectCounter[number_of_recorded_counters][5];
+		unsigned int _objectCounterPointer;
+
+		// the latched playfield output
+		uint8_t _playfieldOutput, _nextPlayfieldOutput;
 
 		// player registers
 		uint8_t _playerColour[2];
-		uint8_t _playerReflection[2];
-		uint8_t _playerGraphicsLatch[2], _playerGraphics[2];
-		uint8_t _playerGraphicsLatchEnable[2];
+		uint8_t _playerReflectionMask[2];
+		uint8_t _playerGraphics[2][2];
+		uint8_t _playerGraphicsSelector[2];
 		bool _playerStart[2];
 
+		// object flags
+		bool _hasSecondCopy[2];
+		bool _hasThirdCopy[2];
+		bool _hasFourthCopy[2];
+		uint8_t _objectMotion[5];		// the value stored to this counter's motion register
+
 		// player + missile registers
 		uint8_t _playerAndMissileSize[2];
 
 		// missile registers
-		uint8_t _missileGraphicsEnable[2], _missileGraphicsReset[2];
+		uint8_t _missileGraphicsEnable[2];
+		bool _missileGraphicsReset[2];
 
 		// ball registers
-		uint8_t _ballGraphicsEnable, _ballGraphicsEnableLatch;
-		uint8_t _ballGraphicsEnableDelay;
+		uint8_t _ballGraphicsEnable[2];
+		uint8_t _ballGraphicsSelector;
 
 		// graphics output
-		int32_t _horizontalTimer;
+		unsigned int _horizontalTimer;
 		bool _vSyncEnabled, _vBlankEnabled;
-		bool _vBlankExtend;
+
+		// horizontal motion control
 		uint8_t _hMoveCounter;
-		bool _hMoveIsCounting, _hMoveWillCount;
-		uint8_t _objectCounter[5], _objectMotion[5];
 		uint8_t _hMoveFlags;
 
 		// joystick state
@@ -82,21 +167,28 @@ class Machine: public CPU6502::Processor<Machine> {
 		// collisions
 		uint8_t _collisions[8];
 
-		enum OutputState {
-			Sync,
-			Blank,
-			ColourBurst,
-			Pixel
-		};
-
 		void output_pixels(unsigned int count);
-		void get_output_pixel(uint8_t *pixel, int offset);
+		uint8_t get_output_pixel();
+		void update_timers(int mask);
+
+		// outputs
 		Outputs::CRT::CRT *_crt;
+		Speaker _speaker;
+
+		// speaker backlog accumlation counter
+		unsigned int _cycles_since_speaker_update;
+		void update_audio();
 
 		// latched output state
 		unsigned int _lastOutputStateDuration;
+		OutputState _stateByExtendTime[2][57];
+		OutputState *_stateByTime;
 		OutputState _lastOutputState;
 		uint8_t *_outputBuffer;
+
+		// lookup table for collision reporting
+		uint8_t _reportedCollisions[64][8];
+		void setup_reported_collisions();
 };
 
 }
diff --git a/Machines/CRTMachine.hpp b/Machines/CRTMachine.hpp
new file mode 100644
index 000000000..235e1e10b
--- /dev/null
+++ b/Machines/CRTMachine.hpp
@@ -0,0 +1,30 @@
+//
+//  CRTMachine.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 31/05/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef CRTMachine_hpp
+#define CRTMachine_hpp
+
+#include "../Outputs/CRT/CRT.hpp"
+#include "../Outputs/Speaker.hpp"
+
+namespace CRTMachine {
+
+class Machine {
+	public:
+		virtual void setup_output(float aspect_ratio) = 0;
+		virtual void close_output() = 0;
+
+		virtual Outputs::CRT::CRT *get_crt() = 0;
+		virtual Outputs::Speaker *get_speaker() = 0;
+
+		virtual void run_for_cycles(int number_of_cycles) = 0;
+};
+
+}
+
+#endif /* CRTMachine_hpp */
diff --git a/Machines/Electron/Electron.cpp b/Machines/Electron/Electron.cpp
index ff1b5ab93..af60bb8de 100644
--- a/Machines/Electron/Electron.cpp
+++ b/Machines/Electron/Electron.cpp
@@ -450,7 +450,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 	return cycles;
 }
 
-void Machine::update_output()
+void Machine::synchronise()
 {
 	update_display();
 	update_audio();
diff --git a/Machines/Electron/Electron.hpp b/Machines/Electron/Electron.hpp
index 151cdbe54..d249bac0d 100644
--- a/Machines/Electron/Electron.hpp
+++ b/Machines/Electron/Electron.hpp
@@ -10,9 +10,8 @@
 #define Electron_hpp
 
 #include "../../Processors/6502/CPU6502.hpp"
-#include "../../Outputs/CRT/CRT.hpp"
-#include "../../Outputs/Speaker.hpp"
 #include "../../Storage/Tape/Tape.hpp"
+#include "../CRTMachine.hpp"
 #include <stdint.h>
 
 namespace Electron {
@@ -142,30 +141,34 @@ class Speaker: public ::Outputs::Filter<Speaker> {
 	@discussion An instance of Electron::Machine represents the current state of an
 	Acorn Electron.
 */
-class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
+class Machine: public CPU6502::Processor<Machine>, public CRTMachine::Machine, Tape::Delegate {
 
 	public:
 
 		Machine();
 
-		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
-
 		void set_rom(ROMSlot slot, size_t length, const uint8_t *data);
 		void set_tape(std::shared_ptr<Storage::Tape> tape);
 
 		void set_key_state(Key key, bool isPressed);
 		void clear_all_keys();
 
-		void setup_output(float aspect_ratio);
-		void close_output();
-		Outputs::CRT::CRT *get_crt() { return _crt.get(); }
-		Outputs::Speaker *get_speaker() { return &_speaker; }
-
-		virtual void tape_did_change_interrupt_status(Tape *tape);
-
-		void update_output();
 		inline void set_use_fast_tape_hack(bool activate) { _use_fast_tape_hack = activate; }
 
+		// to satisfy CPU6502::Processor
+		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
+		void synchronise();
+
+		// to satisfy CRTMachine::Machine
+		virtual void setup_output(float aspect_ratio);
+		virtual void close_output();
+		virtual Outputs::CRT::CRT *get_crt() { return _crt.get(); }
+		virtual Outputs::Speaker *get_speaker() { return &_speaker; }
+		virtual void run_for_cycles(int number_of_cycles) { CPU6502::Processor<Machine>::run_for_cycles(number_of_cycles); }
+
+		// to satisfy Tape::Delegate
+		virtual void tape_did_change_interrupt_status(Tape *tape);
+
 	private:
 
 		inline void update_display();
@@ -215,12 +218,12 @@ class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
 		uint8_t *_current_output_target, *_initial_output_target;
 		unsigned int _current_output_divider;
 
-		// Tape.
+		// Tape
 		Tape _tape;
 		bool _use_fast_tape_hack;
 		bool _fast_load_is_in_data;
 
-		// Outputs.
+		// Outputs
 		std::unique_ptr<Outputs::CRT::CRT> _crt;
 		Speaker _speaker;
 };
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 5b2fa6348..f9dac9acd 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -334,6 +334,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		4B046DC31CFE651500E9E45E /* CRTMachine.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CRTMachine.hpp; sourceTree = "<group>"; };
 		4B0B6E121C9DBD5D00FFB60D /* CRTConstants.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = CRTConstants.hpp; sourceTree = "<group>"; };
 		4B0CCC421C62D0B3001CAC5F /* CRT.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = CRT.cpp; sourceTree = "<group>"; };
 		4B0CCC431C62D0B3001CAC5F /* CRT.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CRT.hpp; sourceTree = "<group>"; };
@@ -1192,6 +1193,7 @@
 			children = (
 				4B2E2D961C3A06EC00138695 /* Atari2600 */,
 				4B2E2D9E1C3A070900138695 /* Electron */,
+				4B046DC31CFE651500E9E45E /* CRTMachine.hpp */,
 			);
 			name = Machines;
 			path = ../../Machines;
diff --git a/OSBindings/Mac/Clock Signal/Documents/Atari2600Document.swift b/OSBindings/Mac/Clock Signal/Documents/Atari2600Document.swift
index 6c586c360..e13fff8fa 100644
--- a/OSBindings/Mac/Clock Signal/Documents/Atari2600Document.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/Atari2600Document.swift	
@@ -10,17 +10,17 @@ import Cocoa
 
 class Atari2600Document: MachineDocument {
 
+	private var atari2600 = CSAtari2600()
+	override func machine() -> CSMachine? {
+		return atari2600
+	}
+
 	// MARK: NSDocument overrides
 	override init() {
 		super.init()
 		self.intendedCyclesPerSecond = 1194720
 	}
 
-	override func windowControllerDidLoadNib(aController: NSWindowController) {
-		super.windowControllerDidLoadNib(aController)
-		atari2600.setView(openGLView, aspectRatio: 4.0 / 3.0)
-	}
-
 	override class func autosavesInPlace() -> Bool {
 		return true
 	}
@@ -31,7 +31,6 @@ class Atari2600Document: MachineDocument {
 		return "Atari2600Document"
 	}
 
-	private var atari2600 = CSAtari2600()
 	override func dataOfType(typeName: String) throws -> NSData {
 		// Insert code here to write your document to data of the specified type. If outError != nil, ensure that you create and set an appropriate error when returning nil.
 		// You can also choose to override fileWrapperOfType:error:, writeToURL:ofType:error:, or writeToURL:ofType:forSaveOperation:originalContentsURL:error: instead.
@@ -42,21 +41,6 @@ class Atari2600Document: MachineDocument {
 		atari2600.setROM(data)
 	}
 
-	override func close() {
-		super.close()
-		openGLView.invalidate()
-	}
-
-	// MARK: MachineDocument overrides
-
-	override func runForNumberOfCycles(numberOfCycles: Int32) {
-		atari2600.runForNumberOfCycles(numberOfCycles)
-	}
-
-	override func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
-		atari2600.drawViewForPixelSize(view.backingSize, onlyIfDirty: onlyIfDirty)
-	}
-
 	// MARK: CSOpenGLViewResponderDelegate
 
 	private func inputForKey(event: NSEvent) -> Atari2600DigitalInput? {
diff --git a/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift b/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift
index 4d08e603a..9f73af395 100644
--- a/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/ElectronDocument.swift	
@@ -12,21 +12,26 @@ import AudioToolbox
 class ElectronDocument: MachineDocument {
 
 	private lazy var electron = CSElectron()
+	override func machine() -> CSMachine! {
+		return electron
+	}
+
+	override func aspectRatio() -> NSSize {
+		return NSSize(width: 11.0, height: 10.0)
+	}
 
 	override func windowControllerDidLoadNib(aController: NSWindowController) {
 		super.windowControllerDidLoadNib(aController)
+
 		self.intendedCyclesPerSecond = 2000000
-		aController.window?.contentAspectRatio = NSSize(width: 11.0, height: 10.0)
-		openGLView.performWithGLContext({
-			if let osPath = NSBundle.mainBundle().pathForResource("os", ofType: "rom") {
-				self.electron.setOSROM(NSData(contentsOfFile: osPath)!)
-			}
-			if let basicPath = NSBundle.mainBundle().pathForResource("basic", ofType: "rom") {
-				self.electron.setBASICROM(NSData(contentsOfFile: basicPath)!)
-			}
-			self.electron.setView(self.openGLView, aspectRatio: 11.0 / 10.0)
-			self.electron.audioQueue = self.audioQueue
-		})
+
+		if let osPath = NSBundle.mainBundle().pathForResource("os", ofType: "rom") {
+			self.electron.setOSROM(NSData(contentsOfFile: osPath)!)
+		}
+		if let basicPath = NSBundle.mainBundle().pathForResource("basic", ofType: "rom") {
+			self.electron.setBASICROM(NSData(contentsOfFile: basicPath)!)
+		}
+
 		establishStoredOptions()
 	}
 
@@ -58,19 +63,6 @@ class ElectronDocument: MachineDocument {
 		electron.setROM(data, slot: 15)
 	}
 
-	lazy var actionLock = NSLock()
-	lazy var drawLock = NSLock()
-	override func close() {
-		actionLock.lock()
-		drawLock.lock()
-		openGLView.invalidate()
-		openGLView.openGLContext!.makeCurrentContext()
-		actionLock.unlock()
-		drawLock.unlock()
-
-		super.close()
-	}
-
 	// MARK: IBActions
 	@IBOutlet var displayTypeButton: NSPopUpButton!
 	@IBAction func setDisplayType(sender: NSPopUpButton!) {
@@ -102,21 +94,6 @@ class ElectronDocument: MachineDocument {
 		self.displayTypeButton.selectItemAtIndex(displayType)
 	}
 
-	// MARK: CSOpenGLViewDelegate
-	override func runForNumberOfCycles(numberOfCycles: Int32) {
-		if actionLock.tryLock() {
-			electron.runForNumberOfCycles(numberOfCycles)
-			actionLock.unlock()
-		}
-	}
-
-	override func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
-		if drawLock.tryLock() {
-			electron.drawViewForPixelSize(view.backingSize, onlyIfDirty: onlyIfDirty)
-			drawLock.unlock()
-		}
-	}
-
 	// MARK: NSWindowDelegate
 	func windowDidResignKey(notification: NSNotification) {
 		electron.clearAllKeys()
diff --git a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift
index 473e81aad..e752f032f 100644
--- a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
@@ -11,6 +11,16 @@ import AudioToolbox
 
 class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDelegate, NSWindowDelegate {
 
+	lazy var actionLock = NSLock()
+	lazy var drawLock = NSLock()
+	func machine() -> CSMachine! {
+		return nil
+	}
+
+	func aspectRatio() -> NSSize {
+		return NSSize(width: 4.0, height: 3.0)
+	}
+
 	@IBOutlet weak var openGLView: CSOpenGLView! {
 		didSet {
 			openGLView.delegate = self
@@ -23,13 +33,35 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
 		optionsPanel?.setIsVisible(true)
 	}
 
-	lazy var audioQueue = AudioQueue()
+	var audioQueue : AudioQueue! = nil
 
 	override func windowControllerDidLoadNib(aController: NSWindowController) {
 		super.windowControllerDidLoadNib(aController)
 
-		// bind the content aspect ratio to remain 4:3 from now on
-		aController.window?.contentAspectRatio = NSSize(width: 4.0, height: 3.0)
+		// establish the output aspect ratio and audio
+		let displayAspectRatio = self.aspectRatio()
+		aController.window?.contentAspectRatio = displayAspectRatio
+		openGLView.performWithGLContext({
+			self.machine().setView(self.openGLView, aspectRatio: Float(displayAspectRatio.width / displayAspectRatio.height))
+		})
+
+		// establish and provide the audio queue, taking advice as to an appropriate sampling rate
+		let maximumSamplingRate = AudioQueue.preferredSamplingRate()
+		let selectedSamplingRate = self.machine().idealSamplingRateFromRange(NSRange(location: 0, length: NSInteger(maximumSamplingRate)))
+		audioQueue = AudioQueue(samplingRate: Float64(selectedSamplingRate))
+		self.machine().audioQueue = self.audioQueue
+		self.machine().setAudioSamplingRate(selectedSamplingRate)
+	}
+
+	override func close() {
+		actionLock.lock()
+		drawLock.lock()
+		openGLView.invalidate()
+		openGLView.openGLContext!.makeCurrentContext()
+		actionLock.unlock()
+		drawLock.unlock()
+
+		super.close()
 	}
 
 	var intendedCyclesPerSecond: Int64 = 0
@@ -54,16 +86,29 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
 				skippedFrames = 0
 			}
 
-			if skippedFrames > 4 {
-				numberOfCycles = min(numberOfCycles, Int64(Double(intendedCyclesPerSecond) * frequency))
-			}
+			// run for at most three frames up to and until that causes overshoots in the
+			// permitted processing window for at least four consecutive frames, in which
+			// case limit to one
+			numberOfCycles = min(numberOfCycles, Int64(Double(intendedCyclesPerSecond) * frequency * ((skippedFrames > 4) ? 3.0 : 1.0)))
 			runForNumberOfCycles(Int32(numberOfCycles))
 		}
 		lastTime = time
 	}
 
-	func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {}
-	func runForNumberOfCycles(numberOfCycles: Int32) {}
+	// MARK: CSOpenGLViewDelegate
+	func runForNumberOfCycles(numberOfCycles: Int32) {
+		if actionLock.tryLock() {
+			self.machine().runForNumberOfCycles(numberOfCycles)
+			actionLock.unlock()
+		}
+	}
+
+	func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
+		if drawLock.tryLock() {
+			self.machine().drawViewForPixelSize(view.backingSize, onlyIfDirty: onlyIfDirty)
+			drawLock.unlock()
+		}
+	}
 
 	// MARK: CSOpenGLViewResponderDelegate
 	func keyDown(event: NSEvent) {}
diff --git a/OSBindings/Mac/Clock Signal/Views/CSOpenGLView.m b/OSBindings/Mac/Clock Signal/Views/CSOpenGLView.m
index ea66b245c..ce4a19046 100644
--- a/OSBindings/Mac/Clock Signal/Views/CSOpenGLView.m	
+++ b/OSBindings/Mac/Clock Signal/Views/CSOpenGLView.m	
@@ -14,6 +14,7 @@
 	CVDisplayLinkRef _displayLink;
 	uint32_t _updateIsOngoing;
 	BOOL _hasSkipped;
+	dispatch_queue_t _serialDispatchQueue;
 }
 
 - (void)prepareOpenGL
@@ -33,6 +34,10 @@
 	CGLPixelFormatObj cglPixelFormat = [[self pixelFormat] CGLPixelFormatObj];
 	CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(_displayLink, cglContext, cglPixelFormat);
 
+	// create a serial dispatch queue
+	_serialDispatchQueue = dispatch_queue_create("OpenGLView", DISPATCH_QUEUE_SERIAL);
+//	dispatch_set_target_queue(_serialDispatchQueue, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0));
+
 	// set the clear colour
 	[self.openGLContext makeCurrentContext];
 	glClearColor(0.0, 0.0, 0.0, 1.0);
@@ -51,31 +56,25 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 - (void)drawAtTime:(const CVTimeStamp *)now frequency:(double)frequency
 {
 	const uint32_t processingMask = 0x01;
-	const uint32_t drawingMask = 0x02;
 
-	// Always post a -openGLView:didUpdateToTime:. This is the hook upon which the substantial processing occurs.
+	// Always post an -openGLView:didUpdateToTime: if a previous one isn't still ongoing. This is the hook upon which the substantial processing occurs.
 	if(!OSAtomicTestAndSet(processingMask, &_updateIsOngoing))
 	{
 		CVTimeStamp time = *now;
 		BOOL didSkip = _hasSkipped;
-		dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
+		dispatch_async(_serialDispatchQueue, ^{
 			[self.delegate openGLView:self didUpdateToTime:time didSkipPreviousUpdate:didSkip frequency:frequency];
-			[self drawViewOnlyIfDirty:YES];
 			OSAtomicTestAndClear(processingMask, &_updateIsOngoing);
 		});
 		_hasSkipped = NO;
-	} else _hasSkipped = YES;
-
-	// Draw the display only if a previous draw is not still ongoing. -drawViewOnlyIfDirty: is guaranteed
-	// to be safe to call concurrently with -openGLView:updateToTime: so there's no need to worry about
-	// the above interrupting the below or vice versa.
-	if(!OSAtomicTestAndSet(drawingMask, &_updateIsOngoing) && _hasSkipped)
-	{
-		dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
-			[self drawViewOnlyIfDirty:YES];
-			OSAtomicTestAndClear(drawingMask, &_updateIsOngoing);
-		});
 	}
+	else
+	{
+		_hasSkipped = YES;
+	}
+
+	// Draw the display now regardless of other activity.
+	[self drawViewOnlyIfDirty:YES];
 }
 
 - (void)invalidate
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.h b/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.h
index cf96e1166..de14ea68b 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.h	
@@ -10,6 +10,11 @@
 
 @interface AudioQueue : NSObject
 
+- (instancetype)initWithSamplingRate:(Float64)samplingRate;
 - (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(size_t)lengthInSamples;
 
+@property (nonatomic, readonly) Float64 samplingRate;
+
++ (Float64)preferredSamplingRate;
+
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m b/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m
index 80f14d7e0..9a409ea60 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m	
@@ -11,7 +11,7 @@
 
 #define AudioQueueNumAudioBuffers	4
 #define AudioQueueStreamLength		1024
-#define AudioQueueBufferLength		256
+#define AudioQueueBufferLength		512
 
 enum {
 	AudioQueueCanProceed,
@@ -85,20 +85,21 @@ static void audioOutputCallback(
 	[(__bridge AudioQueue *)inUserData audioQueue:inAQ didCallbackWithBuffer:inBuffer];
 }
 
-- (instancetype)init
+- (instancetype)initWithSamplingRate:(Float64)samplingRate
 {
 	self = [super init];
 
 	if(self)
 	{
 		_writeLock = [[NSConditionLock alloc] initWithCondition:AudioQueueCanProceed];
+		_samplingRate = samplingRate;
 
 		/*
 			Describe a mono, 16bit, 44.1Khz audio format
 		*/
 		AudioStreamBasicDescription outputDescription;
 
-		outputDescription.mSampleRate = 44100;
+		outputDescription.mSampleRate = samplingRate;
 
 		outputDescription.mFormatID = kAudioFormatLinearPCM;
 		outputDescription.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger;
@@ -113,13 +114,13 @@ static void audioOutputCallback(
 
 		// create an audio output queue along those lines
 		if(!AudioQueueNewOutput(
-			&outputDescription,
-			audioOutputCallback,
-			(__bridge void *)(self),
-			NULL,
-			kCFRunLoopCommonModes,
-			0,
-			&_audioQueue))
+				&outputDescription,
+				audioOutputCallback,
+				(__bridge void *)(self),
+				NULL,
+				kCFRunLoopCommonModes,
+				0,
+				&_audioQueue))
 		{
 			UInt32 bufferBytes = AudioQueueBufferLength * sizeof(int16_t);
 
@@ -139,6 +140,11 @@ static void audioOutputCallback(
 	return self;
 }
 
+- (instancetype)init
+{
+	return [self initWithSamplingRate:[[self class] preferredSamplingRate]];
+}
+
 - (void)dealloc
 {
 	[_writeLock lock];
@@ -190,4 +196,28 @@ static void audioOutputCallback(
 	return ((_audioStreamWritePosition - _audioStreamReadPosition) < (AudioQueueStreamLength - AudioQueueBufferLength)) ? AudioQueueCanProceed : AudioQueueWait;
 }
 
++ (AudioDeviceID)defaultOutputDevice
+{
+	AudioObjectPropertyAddress address;
+	address.mSelector = kAudioHardwarePropertyDefaultOutputDevice;
+	address.mScope = kAudioObjectPropertyScopeGlobal;
+	address.mElement = kAudioObjectPropertyElementMaster;
+
+	AudioDeviceID deviceID;
+	UInt32 size = sizeof(AudioDeviceID);
+	return AudioHardwareServiceGetPropertyData(kAudioObjectSystemObject, &address, 0, NULL, &size, &deviceID) ? 0 : deviceID;
+}
+
++ (Float64)preferredSamplingRate
+{
+	AudioObjectPropertyAddress address;
+	address.mSelector = kAudioDevicePropertyNominalSampleRate;
+	address.mScope = kAudioObjectPropertyScopeGlobal;
+	address.mElement = kAudioObjectPropertyElementMaster;
+
+	Float64 samplingRate;
+	UInt32 size = sizeof(Float64);
+	return AudioHardwareServiceGetPropertyData([self defaultOutputDevice], &address, 0, NULL, &size, &samplingRate) ? 0.0 : samplingRate;
+}
+
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.h b/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.h
index c0e097c52..05a0b70c3 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.h	
@@ -15,6 +15,4 @@
 - (void)setState:(BOOL)state forDigitalInput:(Atari2600DigitalInput)digitalInput;
 - (void)setResetLineEnabled:(BOOL)enabled;
 
-- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty;
-
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.mm b/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.mm
index 4dab3724c..cec8e85bf 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.mm	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSAtari2600.mm	
@@ -49,16 +49,6 @@ struct CRTDelegate: public Outputs::CRT::Delegate {
 	}
 }
 
-- (void)runForNumberOfCycles:(int)numberOfCycles {
-	@synchronized(self) {
-		_atari2600.run_for_cycles(numberOfCycles);
-	}
-}
-
-- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty {
-	_atari2600.get_crt()->draw_frame((unsigned int)pixelSize.width, (unsigned int)pixelSize.height, onlyIfDirty ? true : false);
-}
-
 - (void)setROM:(NSData *)rom {
 	@synchronized(self) {
 		_atari2600.set_rom(rom.length, (const uint8_t *)rom.bytes);
@@ -79,16 +69,14 @@ struct CRTDelegate: public Outputs::CRT::Delegate {
 
 - (void)setupOutputWithAspectRatio:(float)aspectRatio {
 	@synchronized(self) {
-		_atari2600.setup_output(aspectRatio);
+		[super setupOutputWithAspectRatio:aspectRatio];
 		_atari2600.get_crt()->set_delegate(&_crtDelegate);
 		_crtDelegate.atari2600 = self;
 	}
 }
 
-- (void)closeOutput {
-	@synchronized(self) {
-		_atari2600.close_output();
-	}
+- (CRTMachine::Machine * const)machine {
+	return &_atari2600;
 }
 
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h
index 3b4d45ff3..04d8e51ac 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.h	
@@ -19,8 +19,6 @@
 - (void)setKey:(uint16_t)key isPressed:(BOOL)isPressed;
 - (void)clearAllKeys;
 
-- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty;
-
 @property (nonatomic, assign) BOOL useFastLoadingHack;
 @property (nonatomic, assign) BOOL useTelevisionOutput;
 
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm
index bb8ec8c12..c7b82425e 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm	
@@ -16,11 +16,8 @@
 	Electron::Machine _electron;
 }
 
-- (void)runForNumberOfCycles:(int)numberOfCycles {
-	@synchronized(self) {
-		_electron.run_for_cycles(numberOfCycles);
-		_electron.update_output();
-	}
+- (CRTMachine::Machine * const)machine {
+	return &_electron;
 }
 
 - (void)setOSROM:(nonnull NSData *)rom {
@@ -41,10 +38,6 @@
 	}
 }
 
-- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty {
-	_electron.get_crt()->draw_frame((unsigned int)pixelSize.width, (unsigned int)pixelSize.height, onlyIfDirty ? true : false);
-}
-
 - (BOOL)openUEFAtURL:(NSURL *)URL {
 	@synchronized(self) {
 		try {
@@ -57,24 +50,13 @@
 	}
 }
 
-- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(int)sampleRate {
+- (void)clearAllKeys {
 	@synchronized(self) {
-		_electron.get_speaker()->set_output_rate(sampleRate, 256);
-		_electron.get_speaker()->set_delegate(delegate);
-		return YES;
+		_electron.clear_all_keys();
 	}
 }
 
-- (void)clearAllKeys {
-//	dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
-		@synchronized(self) {
-			_electron.clear_all_keys();
-		}
-//	});
-}
-
 - (void)setKey:(uint16_t)key isPressed:(BOOL)isPressed {
-//	dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
 	@synchronized(self) {
 		switch(key)
 		{
@@ -152,16 +134,13 @@
 			break;
 		}
 	}
-//	});
 }
 
 - (void)setUseFastLoadingHack:(BOOL)useFastLoadingHack {
-//	dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
-		@synchronized(self) {
-			_useFastLoadingHack = useFastLoadingHack;
-			_electron.set_use_fast_tape_hack(useFastLoadingHack ? true : false);
-		}
-//	});
+	@synchronized(self) {
+		_useFastLoadingHack = useFastLoadingHack;
+		_electron.set_use_fast_tape_hack(useFastLoadingHack ? true : false);
+	}
 }
 
 - (void)setUseTelevisionOutput:(BOOL)useTelevisionOutput {
@@ -171,16 +150,4 @@
 	}
 }
 
-- (void)setupOutputWithAspectRatio:(float)aspectRatio {
-	@synchronized(self) {
-		_electron.setup_output(aspectRatio);
-	}
-}
-
-- (void)closeOutput {
-	@synchronized(self) {
-		_electron.close_output();
-	}
-}
-
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine+Subclassing.h b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine+Subclassing.h
index 96d090697..59f724bb2 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine+Subclassing.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine+Subclassing.h	
@@ -7,16 +7,15 @@
 //
 
 #import "CSMachine.h"
-#include "CRT.hpp"
-#include "Speaker.hpp"
+#include "CRTMachine.hpp"
 
 @interface CSMachine (Subclassing)
 
-- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(int)sampleRate;
-- (void)speaker:(Outputs::Speaker *)speaker didCompleteSamples:(const int16_t *)samples length:(int)length;
 - (void)performAsync:(dispatch_block_t)action;
 - (void)performSync:(dispatch_block_t)action;
+
+- (CRTMachine::Machine * const)machine;
+
 - (void)setupOutputWithAspectRatio:(float)aspectRatio;
-- (void)closeOutput;
 
 @end
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.h b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.h
index 89467de11..c91487b7f 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.h	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.h	
@@ -13,7 +13,12 @@
 @interface CSMachine : NSObject
 
 - (void)runForNumberOfCycles:(int)numberOfCycles;
+
+- (int)idealSamplingRateFromRange:(NSRange)range;
+- (void)setAudioSamplingRate:(int)samplingRate;
+
 - (void)setView:(CSOpenGLView *)view aspectRatio:(float)aspectRatio;
+- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty;
 
 @property (nonatomic, weak) AudioQueue *audioQueue;
 @property (nonatomic, readonly) CSOpenGLView *view;
diff --git a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.mm b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.mm
index 7c5507218..a52d68bec 100644
--- a/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.mm	
+++ b/OSBindings/Mac/Clock Signal/Wrappers/CSMachine.mm	
@@ -9,6 +9,10 @@
 #import "CSMachine.h"
 #import "CSMachine+Subclassing.h"
 
+@interface CSMachine()
+- (void)speaker:(Outputs::Speaker *)speaker didCompleteSamples:(const int16_t *)samples length:(int)length;
+@end
+
 struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 	__weak CSMachine *machine;
 	void speaker_did_complete_samples(Outputs::Speaker *speaker, const int16_t *buffer, int buffer_size) {
@@ -30,8 +34,6 @@ struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 
 	if(self) {
 		_serialDispatchQueue = dispatch_queue_create("Machine queue", DISPATCH_QUEUE_SERIAL);
-		_speakerDelegate.machine = self;
-		[self setSpeakerDelegate:&_speakerDelegate sampleRate:44100];
 	}
 
 	return self;
@@ -39,15 +41,48 @@ struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 
 - (void)dealloc {
 	[_view performWithGLContext:^{
-		[self closeOutput];
+		@synchronized(self) {
+			self.machine->close_output();
+		}
 	}];
 }
 
-- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(int)sampleRate {
-	return NO;
+- (int)idealSamplingRateFromRange:(NSRange)range {
+	@synchronized(self) {
+		Outputs::Speaker *speaker = self.machine->get_speaker();
+		if(speaker)
+		{
+			return speaker->get_ideal_clock_rate_in_range((int)range.location, (int)(range.location + range.length));
+		}
+		return (int)range.location;
+	}
 }
 
-- (void)runForNumberOfCycles:(int)numberOfCycles {}
+- (void)setAudioSamplingRate:(int)samplingRate {
+	@synchronized(self) {
+		_speakerDelegate.machine = self;
+		[self setSpeakerDelegate:&_speakerDelegate sampleRate:samplingRate];
+	}
+}
+
+- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(int)sampleRate {
+	@synchronized(self) {
+		Outputs::Speaker *speaker = self.machine->get_speaker();
+		if(speaker)
+		{
+			speaker->set_output_rate(sampleRate, 512);
+			speaker->set_delegate(delegate);
+			return YES;
+		}
+		return NO;
+	}
+}
+
+- (void)runForNumberOfCycles:(int)numberOfCycles {
+	@synchronized(self) {
+		self.machine->run_for_cycles(numberOfCycles);
+	}
+}
 
 - (void)performSync:(dispatch_block_t)action {
 	dispatch_sync(_serialDispatchQueue, action);
@@ -57,10 +92,6 @@ struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 	dispatch_async(_serialDispatchQueue, action);
 }
 
-- (void)setupOutputWithAspectRatio:(float)aspectRatio {}
-
-- (void)closeOutput {}
-
 - (void)setView:(CSOpenGLView *)view aspectRatio:(float)aspectRatio {
 	_view = view;
 	[view performWithGLContext:^{
@@ -68,4 +99,13 @@ struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 	}];
 }
 
+- (void)setupOutputWithAspectRatio:(float)aspectRatio {
+	self.machine->setup_output(aspectRatio);
+}
+
+- (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty {
+	self.machine->get_crt()->draw_frame((unsigned int)pixelSize.width, (unsigned int)pixelSize.height, onlyIfDirty ? true : false);
+}
+
+
 @end
diff --git a/Outputs/CRT/Internals/CRTOpenGL.cpp b/Outputs/CRT/Internals/CRTOpenGL.cpp
index 94df2e3b6..e01ea78a5 100644
--- a/Outputs/CRT/Internals/CRTOpenGL.cpp
+++ b/Outputs/CRT/Internals/CRTOpenGL.cpp
@@ -108,6 +108,7 @@ namespace {
 
 OpenGLOutputBuilder::OpenGLOutputBuilder(unsigned int buffer_depth) :
 	_output_mutex(new std::mutex),
+	_draw_mutex(new std::mutex),
 	_visible_area(Rect(0, 0, 1, 1)),
 	_composite_src_output_y(0),
 	_cleared_composite_output_y(0),
@@ -172,8 +173,8 @@ OpenGLOutputBuilder::~OpenGLOutputBuilder()
 
 void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int output_height, bool only_if_dirty)
 {
-	// lock down any further work on the current frame
-	_output_mutex->lock();
+	// lock down any other draw_frames
+	_draw_mutex->lock();
 
 	// establish essentials
 	if(!output_shader_program)
@@ -195,21 +196,6 @@ void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int out
 		glDeleteSync(_fence);
 	}
 
-	// release the mapping, giving up on trying to draw if data has been lost
-	GLsizei submitted_output_data = submitArrayData(output_array_buffer, _output_buffer_data.get(), &_output_buffer_data_pointer);
-
-	// bind and flush the source array buffer
-	GLsizei submitted_source_data = submitArrayData(source_array_buffer, _source_buffer_data.get(), &_source_buffer_data_pointer);
-
-	// determine how many lines are newly reclaimed; they'll need to be cleared
-	Range clearing_zones[2];
-
-	// the clearing zones for the composite output Y are calculated with a fixed offset of '1' which has the effect of clearing
-	// one ahead of the expected drawing area this frame; that's because the current _composite_src_output_y may or may not have been
-	// written to during the last update, so we want it to have been cleared during the last update.
-	int number_of_clearing_zones	= getCircularRanges(&_cleared_composite_output_y, &_composite_src_output_y, IntermediateBufferHeight, 1, 1, clearing_zones);
-	uint16_t completed_texture_y	= _buffer_builder->get_and_finalise_current_line();
-
 	// make sure there's a target to draw to
 	if(!framebuffer || framebuffer->get_height() != output_height || framebuffer->get_width() != output_width)
 	{
@@ -228,6 +214,24 @@ void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int out
 		framebuffer = std::move(new_framebuffer);
 	}
 
+	// lock out the machine emulation until data is copied
+	_output_mutex->lock();
+
+	// release the mapping, giving up on trying to draw if data has been lost
+	GLsizei submitted_output_data = submitArrayData(output_array_buffer, _output_buffer_data.get(), &_output_buffer_data_pointer);
+
+	// bind and flush the source array buffer
+	GLsizei submitted_source_data = submitArrayData(source_array_buffer, _source_buffer_data.get(), &_source_buffer_data_pointer);
+
+	// determine how many lines are newly reclaimed; they'll need to be cleared
+	Range clearing_zones[2];
+
+	// the clearing zones for the composite output Y are calculated with a fixed offset of '1' which has the effect of clearing
+	// one ahead of the expected drawing area this frame; that's because the current _composite_src_output_y may or may not have been
+	// written to during the last update, so we want it to have been cleared during the last update.
+	int number_of_clearing_zones	= getCircularRanges(&_cleared_composite_output_y, &_composite_src_output_y, IntermediateBufferHeight, 1, 1, clearing_zones);
+	uint16_t completed_texture_y	= _buffer_builder->get_and_finalise_current_line();
+
 	// upload new source pixels
 	if(completed_texture_y)
 	{
@@ -239,6 +243,9 @@ void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int out
 							_buffer_builder->get_image_pointer());
 	}
 
+	// data having been grabbed, allow the machine to continue
+	_output_mutex->unlock();
+
 	struct RenderStage {
 		OpenGL::TextureTarget *const target;
 		OpenGL::Shader *const shader;
@@ -330,7 +337,7 @@ void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int out
 	framebuffer->draw((float)output_width / (float)output_height);
 
 	_fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
-	_output_mutex->unlock();
+	_draw_mutex->unlock();
 }
 
 void OpenGLOutputBuilder::reset_all_OpenGL_state()
diff --git a/Outputs/CRT/Internals/CRTOpenGL.hpp b/Outputs/CRT/Internals/CRTOpenGL.hpp
index e562767a8..4f0a79a32 100644
--- a/Outputs/CRT/Internals/CRTOpenGL.hpp
+++ b/Outputs/CRT/Internals/CRTOpenGL.hpp
@@ -58,6 +58,7 @@ class OpenGLOutputBuilder {
 		// the run and input data buffers
 		std::unique_ptr<CRTInputBufferBuilder> _buffer_builder;
 		std::unique_ptr<std::mutex> _output_mutex;
+		std::unique_ptr<std::mutex> _draw_mutex;
 
 		// transient buffers indicating composite data not yet decoded
 		GLsizei _composite_src_output_y, _cleared_composite_output_y;
diff --git a/Outputs/CRT/Internals/Shaders/IntermediateShader.cpp b/Outputs/CRT/Internals/Shaders/IntermediateShader.cpp
index ed82601ea..8d15a1291 100644
--- a/Outputs/CRT/Internals/Shaders/IntermediateShader.cpp
+++ b/Outputs/CRT/Internals/Shaders/IntermediateShader.cpp
@@ -269,7 +269,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_chroma_filter_shade
 				"), vec3(1.0))"
 			");"
 
-			"vec3 lumaChromaColourInRange = (lumaChromaColour - vec3(0.0, 0.5, 0.5)) * vec3(1.0, 4.0, 4.0);"
+			"vec3 lumaChromaColourInRange = (lumaChromaColour - vec3(0.0, 0.5, 0.5)) * vec3(1.0, 2.0, 2.0);"
 			"fragColour = lumaChromaToRGB * lumaChromaColourInRange;"
 		"}", false, false);
 }
diff --git a/Outputs/CRT/Internals/Shaders/OutputShader.cpp b/Outputs/CRT/Internals/Shaders/OutputShader.cpp
index 682e62304..f543853a7 100644
--- a/Outputs/CRT/Internals/Shaders/OutputShader.cpp
+++ b/Outputs/CRT/Internals/Shaders/OutputShader.cpp
@@ -78,7 +78,7 @@ std::unique_ptr<OutputShader> OutputShader::make_shader(const char *fragment_met
 
 		"void main(void)"
 		"{"
-			"fragColour = vec4(%s, 0.5*cos(lateralVarying));"
+			"fragColour = vec4(%s, 0.5);"//*cos(lateralVarying)
 		"}",
 	sampler_type, fragment_methods, colour_expression);
 
diff --git a/Outputs/Speaker.hpp b/Outputs/Speaker.hpp
index 759d04472..9742e86df 100644
--- a/Outputs/Speaker.hpp
+++ b/Outputs/Speaker.hpp
@@ -24,6 +24,18 @@ class Speaker {
 				virtual void speaker_did_complete_samples(Speaker *speaker, const int16_t *buffer, int buffer_size) = 0;
 		};
 
+		int get_ideal_clock_rate_in_range(int minimum, int maximum)
+		{
+			// return exactly the input rate if possible
+			if(_input_cycles_per_second >= minimum && _input_cycles_per_second <= maximum) return _input_cycles_per_second;
+
+			// if the input rate is lower, return the minimum
+			if(_input_cycles_per_second < minimum) return minimum;
+
+			// otherwise, return the maximum
+			return maximum;
+		}
+
 		void set_output_rate(int cycles_per_second, int buffer_size)
 		{
 			_output_cycles_per_second = cycles_per_second;
@@ -76,20 +88,16 @@ template <class T> class Filter: public Speaker {
 		{
 			if(_coefficients_are_dirty) update_filter_coefficients();
 
-			// TODO: what if output rate is greater than input rate?
-
-			// fill up as much of the input buffer as possible
-			while(input_cycles)
+			// if input and output rates exactly match, just accumulate results and pass on
+			if(_input_cycles_per_second == _output_cycles_per_second)
 			{
-				unsigned int cycles_to_read = (unsigned int)std::min((int)input_cycles, _number_of_taps - _input_buffer_depth);
-				static_cast<T *>(this)->get_samples(cycles_to_read, &_input_buffer.get()[_input_buffer_depth]);
-				input_cycles -= cycles_to_read;
-				_input_buffer_depth += cycles_to_read;
-
-				if(_input_buffer_depth == _number_of_taps)
+				while(input_cycles)
 				{
-					_buffer_in_progress.get()[_buffer_in_progress_pointer] = _filter->apply(_input_buffer.get());
-					_buffer_in_progress_pointer++;
+					unsigned int cycles_to_read = (unsigned int)(_buffer_size - _buffer_in_progress_pointer);
+					if(cycles_to_read > input_cycles) cycles_to_read = input_cycles;
+
+					static_cast<T *>(this)->get_samples(cycles_to_read, &_buffer_in_progress.get()[_buffer_in_progress_pointer]);
+					_buffer_in_progress_pointer += cycles_to_read;
 
 					// announce to delegate if full
 					if(_buffer_in_progress_pointer == _buffer_size)
@@ -101,24 +109,60 @@ template <class T> class Filter: public Speaker {
 						}
 					}
 
-					// If the next loop around is going to reuse some of the samples just collected, use a memmove to
-					// preserve them in the correct locations (TODO: use a longer buffer to fix that) and don't skip
-					// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
-					uint64_t steps = _stepper->step();
-					if(steps < _number_of_taps)
+					input_cycles -= cycles_to_read;
+				}
+
+				return;
+			}
+
+			// if the output rate is less than the input rate, use the filter
+			if(_input_cycles_per_second > _output_cycles_per_second)
+			{
+				while(input_cycles)
+				{
+					unsigned int cycles_to_read = (unsigned int)std::min((int)input_cycles, _number_of_taps - _input_buffer_depth);
+					static_cast<T *>(this)->get_samples(cycles_to_read, &_input_buffer.get()[_input_buffer_depth]);
+					input_cycles -= cycles_to_read;
+					_input_buffer_depth += cycles_to_read;
+
+					if(_input_buffer_depth == _number_of_taps)
 					{
-						int16_t *input_buffer = _input_buffer.get();
-						memmove(input_buffer, &input_buffer[steps], sizeof(int16_t)  * ((size_t)_number_of_taps - (size_t)steps));
-						_input_buffer_depth -= steps;
-					}
-					else
-					{
-						if(steps > _number_of_taps)
-							static_cast<T *>(this)->skip_samples((unsigned int)steps - (unsigned int)_number_of_taps);
-						_input_buffer_depth = 0;
+						_buffer_in_progress.get()[_buffer_in_progress_pointer] = _filter->apply(_input_buffer.get());
+						_buffer_in_progress_pointer++;
+
+						// announce to delegate if full
+						if(_buffer_in_progress_pointer == _buffer_size)
+						{
+							_buffer_in_progress_pointer = 0;
+							if(_delegate)
+							{
+								_delegate->speaker_did_complete_samples(this, _buffer_in_progress.get(), _buffer_size);
+							}
+						}
+
+						// If the next loop around is going to reuse some of the samples just collected, use a memmove to
+						// preserve them in the correct locations (TODO: use a longer buffer to fix that) and don't skip
+						// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
+						uint64_t steps = _stepper->step();
+						if(steps < _number_of_taps)
+						{
+							int16_t *input_buffer = _input_buffer.get();
+							memmove(input_buffer, &input_buffer[steps], sizeof(int16_t)  * ((size_t)_number_of_taps - (size_t)steps));
+							_input_buffer_depth -= steps;
+						}
+						else
+						{
+							if(steps > _number_of_taps)
+								static_cast<T *>(this)->skip_samples((unsigned int)steps - (unsigned int)_number_of_taps);
+							_input_buffer_depth = 0;
+						}
 					}
 				}
+
+				return;
 			}
+
+			// TODO: input rate is less than output rate
 		}
 
 	private:
diff --git a/Processors/6502/CPU6502.hpp b/Processors/6502/CPU6502.hpp
index f5d731daa..e4e884a06 100644
--- a/Processors/6502/CPU6502.hpp
+++ b/Processors/6502/CPU6502.hpp
@@ -67,9 +67,12 @@ extern const uint8_t JamOpcode;
 	@abstact An abstract base class for emulation of a 6502 processor via the curiously recurring template pattern/f-bounded polymorphism.
 
 	@discussion Subclasses should implement @c perform_bus_operation(BusOperation operation, uint16_t address, uint8_t *value) in
-	order to provde the bus on which the 6502 operates. Additional functionality can be provided by the host machine by providing
-	a jam handler and inserting jam opcodes where appropriate; that will cause call outs when the program counter reaches those
-	addresses. @c return_from_subroutine can be used to exit from a jammed state.
+	order to provide the bus on which the 6502 operates and @c synchronise(), which is called upon completion of a continuous run
+	of cycles to allow a subclass to bring any on-demand activities up to date.
+
+	Additional functionality can be provided by the host machine by providing a jam handler and inserting jam opcodes where appropriate;
+	that will cause call outs when the program counter reaches those addresses. @c return_from_subroutine can be used to exit from a
+	jammed state.
 */
 template <class T> class Processor {
 	public:
@@ -597,6 +600,7 @@ template <class T> class Processor {
 
 						case CycleFetchOperation: {
 							_lastOperationPC = _pc;
+//							printf("%04x	x:%02x\n", _pc.full, _x);
 							_pc.full++;
 							read_op(_operation, _lastOperationPC.full);
 
@@ -1040,15 +1044,17 @@ template <class T> class Processor {
 						_ready_is_active = true;
 					}
 				}
-
-				_cycles_left_to_run = number_of_cycles;
-				_scheduleProgramsReadPointer = scheduleProgramsReadPointer;
-				_scheduleProgramProgramCounter = scheduleProgramProgramCounter;
-				_nextAddress = nextAddress;
-				_nextBusOperation = nextBusOperation;
-				_busAddress = busAddress;
-				_busValue = busValue;
 			}
+
+			_cycles_left_to_run = number_of_cycles;
+			_scheduleProgramsReadPointer = scheduleProgramsReadPointer;
+			_scheduleProgramProgramCounter = scheduleProgramProgramCounter;
+			_nextAddress = nextAddress;
+			_nextBusOperation = nextBusOperation;
+			_busAddress = busAddress;
+			_busValue = busValue;
+
+			static_cast<T *>(this)->synchronise();
 		}
 
 		/*!