Some AY-3-8910, AY8930 enhancements

Fix AY PSG clock divider function when exists, Update emulation core (MAME AY PSG and compatibles - includes noise routine updates)
Fix configuration flag, Add MSX Darky sound expander to preset

Clock divider isn't affected to expanded mode's tone and noise generator?

src/engine/platform/ay.cpp

@@ -27,7 +27,7 @@
 #define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
 #define immWrite(a,v) if (!skipRegisterWrites) {writes.emplace(regRemap(a),v); if (dumpWrites) {addWrite(regRemap(a),v);} }
 
-#define CHIP_DIVIDER 8
+#define CHIP_DIVIDER ((sunsoft||clockSel)?16:8)
 
 const char* regCheatSheetAY[]={
   "FreqL_A", "0",
@@ -589,6 +589,7 @@ void DivPlatformAY8910::poke(std::vector<DivRegWrite>& wlist) {
 }
 
 void DivPlatformAY8910::setFlags(unsigned int flags) {
+  clockSel=(flags>>7)&1;
   switch (flags&15) {
     case 1:
       chipClock=COLOR_PAL*2.0/5.0;
@@ -620,6 +621,12 @@ void DivPlatformAY8910::setFlags(unsigned int flags) {
     case 10:
       chipClock=2097152;
       break;
+    case 11:
+      chipClock=COLOR_NTSC;
+      break;
+    case 12:
+      chipClock=3600000;
+      break;
     default:
       chipClock=COLOR_NTSC/2.0;
       break;
@@ -653,8 +660,9 @@ void DivPlatformAY8910::setFlags(unsigned int flags) {
       break;
   }
   ay->device_start();
+  ay->set_clock_sel(clockSel);
 
-  stereo=flags>>6;
+  stereo=(flags>>6)&1;
 }
 
 int DivPlatformAY8910::init(DivEngine* p, int channels, int sugRate, unsigned int flags) {

src/engine/platform/ay.h

@@ -70,7 +70,7 @@ class DivPlatformAY8910: public DivDispatch {
     int delay;
 
     bool extMode;
-    bool stereo, sunsoft, intellivision;
+    bool stereo, sunsoft, intellivision, clockSel;
     bool ioPortA, ioPortB;
     unsigned char portAVal, portBVal;
   

src/engine/platform/ay8930.cpp

@@ -27,7 +27,7 @@
 #define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
 #define immWrite2(a,v) if (!skipRegisterWrites) {writes.emplace(a,v); if (dumpWrites) {addWrite(a,v);} }
 
-#define CHIP_DIVIDER 4
+#define CHIP_DIVIDER 8
 
 const char* regCheatSheetAY8930[]={
   "FreqL_A", "00",
@@ -64,7 +64,7 @@ const char* regCheatSheetAY8930[]={
 void DivPlatformAY8930::immWrite(unsigned char a, unsigned char v) {
   if ((int)bank!=(a>>4)) {
     bank=a>>4;
-    immWrite2(0x0d, 0xa0|(bank<<4)|ayEnvMode[0]);
+    immWrite2(0x0d, 0xa0|(bank<<4)|chan[0].envelope.mode);
   }
   if (a==0x0d) {
     immWrite2(0x0d,0xa0|(bank<<4)|(v&15));
@@ -258,8 +258,8 @@ void DivPlatformAY8930::tick(bool sysTick) {
       rWrite(0x16+i,chan[i].std.ex1.val);
     }
     if (chan[i].std.ex2.had) {
-      ayEnvMode[i]=chan[i].std.ex2.val;
+      chan[i].envelope.mode=chan[i].std.ex2.val;
-      rWrite(regMode[i],ayEnvMode[i]);
+      rWrite(regMode[i],chan[i].envelope.mode);
     }
     if (chan[i].std.ex3.had) {
       chan[i].autoEnvNum=chan[i].std.ex3.val;
@@ -296,29 +296,29 @@ void DivPlatformAY8930::tick(bool sysTick) {
       if (chan[i].keyOn) chan[i].keyOn=false;
       if (chan[i].keyOff) chan[i].keyOff=false;
       if (chan[i].freqChanged && chan[i].autoEnvNum>0 && chan[i].autoEnvDen>0) {
-        ayEnvPeriod[i]=(chan[i].freq*chan[i].autoEnvDen/chan[i].autoEnvNum)>>4;
+        chan[i].envelope.period=(chan[i].freq*chan[i].autoEnvDen/chan[i].autoEnvNum)>>4;
-        immWrite(regPeriodL[i],ayEnvPeriod[i]);
+        immWrite(regPeriodL[i],chan[i].envelope.period);
-        immWrite(regPeriodH[i],ayEnvPeriod[i]>>8);
+        immWrite(regPeriodH[i],chan[i].envelope.period>>8);
       }
       chan[i].freqChanged=false;
     }
 
-    if (ayEnvSlide[i]!=0) {
+    if (chan[i].envelope.slide!=0) {
-      ayEnvSlideLow[i]+=ayEnvSlide[i];
+      chan[i].envelope.slideLow+=chan[i].envelope.slide;
-      while (ayEnvSlideLow[i]>7) {
+      while (chan[i].envelope.slideLow>7) {
-        ayEnvSlideLow[i]-=8;
+        chan[i].envelope.slideLow-=8;
-        if (ayEnvPeriod[i]<0xffff) {
+        if (chan[i].envelope.period<0xffff) {
-          ayEnvPeriod[i]++;
+          chan[i].envelope.period++;
-          immWrite(regPeriodL[i],ayEnvPeriod[i]);
+          immWrite(regPeriodL[i],chan[i].envelope.period);
-          immWrite(regPeriodH[i],ayEnvPeriod[i]>>8);
+          immWrite(regPeriodH[i],chan[i].envelope.period>>8);
         }
       }
-      while (ayEnvSlideLow[i]<-7) {
+      while (chan[i].envelope.slideLow<-7) {
-        ayEnvSlideLow[i]+=8;
+        chan[i].envelope.slideLow+=8;
-        if (ayEnvPeriod[i]>0) {
+        if (chan[i].envelope.period>0) {
-          ayEnvPeriod[i]--;
+          chan[i].envelope.period--;
-          immWrite(regPeriodL[i],ayEnvPeriod[i]);
+          immWrite(regPeriodL[i],chan[i].envelope.period);
-          immWrite(regPeriodH[i],ayEnvPeriod[i]>>8);
+          immWrite(regPeriodH[i],chan[i].envelope.period>>8);
         }
       }
     }
@@ -435,8 +435,8 @@ int DivPlatformAY8930::dispatch(DivCommand c) {
       rWrite(0x06,c.value);
       break;
     case DIV_CMD_AY_ENVELOPE_SET:
-      ayEnvMode[c.chan]=c.value>>4;
+      chan[c.chan].envelope.mode=c.value>>4;
-      rWrite(regMode[c.chan],ayEnvMode[c.chan]);
+      rWrite(regMode[c.chan],chan[c.chan].envelope.mode);
       if (c.value&15) {
         chan[c.chan].psgMode|=4;
       } else {
@@ -449,19 +449,19 @@ int DivPlatformAY8930::dispatch(DivCommand c) {
       }
       break;
     case DIV_CMD_AY_ENVELOPE_LOW:
-      ayEnvPeriod[c.chan]&=0xff00;
+      chan[c.chan].envelope.period&=0xff00;
-      ayEnvPeriod[c.chan]|=c.value;
+      chan[c.chan].envelope.period|=c.value;
-      immWrite(regPeriodL[c.chan],ayEnvPeriod[c.chan]);
+      immWrite(regPeriodL[c.chan],chan[c.chan].envelope.period);
-      immWrite(regPeriodH[c.chan],ayEnvPeriod[c.chan]>>8);
+      immWrite(regPeriodH[c.chan],chan[c.chan].envelope.period>>8);
       break;
     case DIV_CMD_AY_ENVELOPE_HIGH:
-      ayEnvPeriod[c.chan]&=0xff;
+      chan[c.chan].envelope.period&=0xff;
-      ayEnvPeriod[c.chan]|=c.value<<8;
+      chan[c.chan].envelope.period|=c.value<<8;
-      immWrite(regPeriodL[c.chan],ayEnvPeriod[c.chan]);
+      immWrite(regPeriodL[c.chan],chan[c.chan].envelope.period);
-      immWrite(regPeriodH[c.chan],ayEnvPeriod[c.chan]>>8);
+      immWrite(regPeriodH[c.chan],chan[c.chan].envelope.period>>8);
       break;
     case DIV_CMD_AY_ENVELOPE_SLIDE:
-      ayEnvSlide[c.chan]=c.value;
+      chan[c.chan].envelope.slide=c.value;
       break;
     case DIV_CMD_AY_NOISE_MASK_AND:
       ayNoiseAnd=c.value;
@@ -526,9 +526,9 @@ void DivPlatformAY8930::muteChannel(int ch, bool mute) {
 void DivPlatformAY8930::forceIns() {
   for (int i=0; i<3; i++) {
     chan[i].insChanged=true;
-    immWrite(regPeriodL[i],ayEnvPeriod[i]);
+    immWrite(regPeriodL[i],chan[i].envelope.period);
-    immWrite(regPeriodH[i],ayEnvPeriod[i]>>8);
+    immWrite(regPeriodH[i],chan[i].envelope.period>>8);
-    immWrite(regMode[i],ayEnvMode[i]);
+    immWrite(regMode[i],chan[i].envelope.mode);
   }
 }
 
@@ -556,10 +556,10 @@ void DivPlatformAY8930::reset() {
     chan[i]=DivPlatformAY8930::Channel();
     chan[i].std.setEngine(parent);
     chan[i].vol=31;
-    ayEnvPeriod[i]=0;
+    chan[i].envelope.period=0;
-    ayEnvMode[i]=0;
+    chan[i].envelope.mode=0;
-    ayEnvSlide[i]=0;
+    chan[i].envelope.slide=0;
-    ayEnvSlideLow[i]=0;
+    chan[i].envelope.slideLow=0;
   }
   if (dumpWrites) {
     addWrite(0xffffffff,0);
@@ -641,16 +641,23 @@ void DivPlatformAY8930::setFlags(unsigned int flags) {
     case 10:
       chipClock=2097152;
       break;
+    case 11:
+      chipClock=COLOR_NTSC;
+      break;
+    case 12:
+      chipClock=3600000;
+      break;
     default:
       chipClock=COLOR_NTSC/2.0;
       break;
   }
-  rate=chipClock/4;
+  rate=chipClock/8;
   for (int i=0; i<3; i++) {
     oscBuf[i]->rate=rate;
   }
 
-  stereo=flags>>6;
+  stereo=(flags>>6)&1;
+  clockSel=(flags>>7)&1;
 }
 
 int DivPlatformAY8930::init(DivEngine* p, int channels, int sugRate, unsigned int flags) {
@@ -664,6 +671,7 @@ int DivPlatformAY8930::init(DivEngine* p, int channels, int sugRate, unsigned in
   setFlags(flags);
   ay=new ay8930_device(rate);
   ay->device_start();
+  ay->set_clock_sel(clockSel);
   ayBufLen=65536;
   for (int i=0; i<3; i++) ayBuf[i]=new short[ayBufLen];
   reset();

src/engine/platform/ay8930.h

@@ -27,6 +27,17 @@
 class DivPlatformAY8930: public DivDispatch {
   protected:
     struct Channel {
+      struct Envelope {
+        unsigned char mode;
+        unsigned short period;
+        short slideLow;
+        short slide;
+        Envelope():
+          mode(0),
+          period(0),
+          slideLow(0),
+          slide(0) {}
+      } envelope;
       unsigned char freqH, freqL;
       int freq, baseFreq, note, pitch, pitch2;
       int ins;
@@ -59,16 +70,12 @@ class DivPlatformAY8930: public DivDispatch {
 
     int delay;
 
-    bool extMode, stereo;
+    bool extMode, stereo, clockSel;
     bool ioPortA, ioPortB;
     unsigned char portAVal, portBVal;
   
     short oldWrites[32];
     short pendingWrites[32];
-    unsigned char ayEnvMode[3];
-    unsigned short ayEnvPeriod[3];
-    short ayEnvSlideLow[3];
-    short ayEnvSlide[3];
     short* ayBuf[3];
     size_t ayBufLen;
 

src/engine/platform/sound/ay8910.cpp

@@ -1021,10 +1021,8 @@ void ay8910_device::ay8910_write_reg(int r, int v)
 			m_tone[2].set_duty(m_regs[AY_CDUTY]);
 			break;
 		case AY_NOISEAND:
-      m_noise_and=m_regs[AY_NOISEAND];
-      break;
 		case AY_NOISEOR:
-      m_noise_or=m_regs[AY_NOISEOR];
+			// No action required
 			break;
 		default:
 			m_regs[r] = 0; // reserved, set as 0
@@ -1047,7 +1045,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 	if (!m_ready)
 	{
 		for (int chan = 0; chan < m_streams; chan++)
-      memset(outputs[chan],0,outLen*sizeof(short));
+			memset(outputs[chan],0,outLen*sizeof(short));
 	}
 
 	/* The 8910 has three outputs, each output is the mix of one of the three */
@@ -1063,8 +1061,8 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 		for (int chan = 0; chan < NUM_CHANNELS; chan++)
 		{
 			tone = &m_tone[chan];
-			const int period = std::max<int>(1,tone->period);
+			const int period = std::max<int>(1,tone->period) << 1;
-			tone->count += is_expanded_mode() ? 16 : (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
+			tone->count += is_expanded_mode() ? 32 : (is_clock_divided() ? 1 : 2);
 			while (tone->count >= period)
 			{
 				tone->duty_cycle = (tone->duty_cycle - 1) & 0x1f;
@@ -1073,48 +1071,35 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 			}
 		}
 
-		m_count_noise++;
+		if ((++m_count_noise) >= noise_period())
-		if (m_count_noise >= noise_period())
 		{
 			/* toggle the prescaler output. Noise is no different to
 			 * channels.
 			 */
 			m_count_noise = 0;
-			m_prescale_noise = (m_prescale_noise + 1) & ((m_feature & PSG_HAS_EXPANDED_MODE) ? 3 : 1);
+			m_prescale_noise = (m_prescale_noise + 1) & (is_clock_divided() ? 3 : 1);
 
-			if (!m_prescale_noise || is_expanded_mode()) // AY8930 noise generator rate is twice compares as compatibility mode
+			if (is_expanded_mode()) // AY8930 noise generator rate is twice? compares as compatibility mode
 			{
-        if (is_expanded_mode()) {
+				// This is called "Noise value" on the docs, but is a counter whose period is determined by the LFSR.
-          // This is called "Noise value" on the docs, but is a counter whose period is determined by the LFSR.
+				// Using AND/OR gates, specific periods can be "filtered" out.
-          // Using AND/OR gates, specific periods can be "filtered" out.
+				// A square wave can be generated through this behavior, which can be used for crude AM pulse width modulation.
-          // A square wave can be generated through this behavior, which can be used for crude AM pulse width modulation.
+
-          
+				// The period of the noise is determined by this value.
-          // The period of the noise is determined by this value.
+				// The least significant byte of the LFSR is bitwise ANDed with the AND mask, and then bitwise ORed with the OR mask.
-          // The least significant byte of the LFSR is bitwise ANDed with the AND mask, and then bitwise ORed with the OR mask.
+				if ((++m_noise_value) >= (((unsigned char)(m_rng) & noise_and()) | noise_or())) // Clock the noise value.
-          unsigned int noiseValuePeriod = ((m_rng & 0xFF & m_noise_and) | m_noise_or);
+				{
-          
+					m_noise_value = 0;
-          // Clock the noise value.
+
-          if (m_noise_value >= noiseValuePeriod) {
+					// When everything is finally said and done, a 1bit latch is flipped.
-              m_noise_value = 0;
+					// This is the final output of the noise, to be multiplied by the tone and envelope generators of the channel.
-              
+					m_noise_out ^= 1;
-              // When everything is finally said and done, a 1bit latch is flipped.
+
-              // This is the final output of the noise, to be multiplied by the tone and envelope generators of the channel.
+					noise_rng_tick();
-              m_noise_latch ^= 1;
+				}
-              
-              // The 17-bit LFSR is updated, using an XOR across bits 0 and 2.
-              unsigned int feedback = (m_rng & 1) ^ ((m_rng >> 2) & 1);
-              m_rng >>= 1;
-              m_rng |= (feedback << 16);
-          }
-          m_noise_value++;
-        } else {
-          /* The Random Number Generator of the 8910 is a 17-bit shift */
-          /* register. The input to the shift register is bit0 XOR bit3 */
-          /* (bit0 is the output). This was verified on AY-3-8910 and YM2149 chips. */
-          m_rng ^= (((m_rng & 1) ^ ((m_rng >> 3) & 1)) << 17);
-          m_rng >>= 1;
-        }
 			}
+			else if (!m_prescale_noise)
+				noise_rng_tick();
 		}
 
 		for (int chan = 0; chan < NUM_CHANNELS; chan++)
@@ -1130,8 +1115,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 			if (envelope->holding == 0)
 			{
 				const int period = envelope->period * m_step;
-				envelope->count++;
+				if ((++envelope->count) >= period)
-				if (envelope->count >= period)
 				{
 					envelope->count = 0;
 					envelope->step--;
@@ -1263,20 +1247,14 @@ void ay8910_device::device_start()
 }
 
 
-void ay8910_device::ay8910_reset_ym(bool ay8930)
+void ay8910_device::ay8910_reset_ym()
 {
 	m_active = false;
 	m_register_latch = 0;
-  if (ay8930) {
+	m_rng = (m_feature & PSG_HAS_EXPANDED_MODE) ? 0x1ffff : 1;
-    m_rng = 0x1ffff;
-  } else {
-	  m_rng = 1;
-  }
 	m_mode = 0; // ay-3-8910 compatible mode
-  m_noise_and = 0xff;
+	m_noise_value = 0;
-  m_noise_or = 0;
+	m_noise_out = 0;
-  m_noise_value = 0;
-  m_noise_latch = 0;
 	for (int chan = 0; chan < NUM_CHANNELS; chan++)
 	{
 		m_tone[chan].reset();
@@ -1335,7 +1313,7 @@ void ay8910_device::ay8910_write_ym(int addr, unsigned char data)
 
 unsigned char ay8910_device::ay8910_read_ym()
 {
-	int r = m_register_latch + get_register_bank();
+	unsigned char r = m_register_latch + get_register_bank();
 
 	if (!m_active) return 0xff; // high impedance
 
@@ -1380,7 +1358,7 @@ unsigned char ay8910_device::ay8910_read_ym()
 
 void ay8910_device::device_reset()
 {
-	ay8910_reset_ym(chip_type == AY8930);
+	ay8910_reset_ym();
 }
 
 /*************************************
@@ -1454,22 +1432,20 @@ ay8910_device::ay8910_device(unsigned int clock)
 ay8910_device::ay8910_device(device_type type, unsigned int clock,
 								psg_type_t psg_type, int streams, int ioports, int feature)
 	: chip_type(type),
-    m_type(psg_type),
+		m_type(psg_type),
 		m_streams(streams),
 		m_ready(0),
 		m_active(false),
 		m_register_latch(0),
 		m_last_enable(0),
 		m_prescale_noise(0),
+		m_noise_value(0),
 		m_count_noise(0),
 		m_rng(0),
-    m_noise_and(0),
+		m_noise_out(0),
-    m_noise_or(0),
-    m_noise_value(0),
-    m_noise_latch(0),
 		m_mode(0),
 		m_env_step_mask((!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 0x0f : 0x1f),
-		m_step(         (feature & PSG_HAS_EXPANDED_MODE) || (psg_type == PSG_TYPE_AY) ? 2 : 1),
+		m_step(         (feature & PSG_HAS_INTERNAL_DIVIDER) || (psg_type == PSG_TYPE_AY) ? 2 : 1),
 		m_zero_is_off(  (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 1 : 0),
 		m_par(          (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param),
 		m_par_env(      (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param_env),
@@ -1494,7 +1470,7 @@ void ay8910_device::set_type(psg_type_t psg_type)
 	if (psg_type == PSG_TYPE_AY)
 	{
 		m_env_step_mask = 0x0f;
-		m_step = 2;
+		m_step = is_clock_divided() ? 4 : 2;
 		m_zero_is_off = 1;
 		m_par = &ay8910_param;
 		m_par_env = &ay8910_param;
@@ -1502,7 +1478,7 @@ void ay8910_device::set_type(psg_type_t psg_type)
 	else
 	{
 		m_env_step_mask = 0x1f;
-		m_step = (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
+		m_step = is_clock_divided() ? 2 : 1;
 		m_zero_is_off = 0;
 		m_par = &ym2149_param;
 		m_par_env = &ym2149_param_env;

src/engine/platform/sound/ay8910.h

@@ -97,7 +97,25 @@ public:
 	void data_w(unsigned char data);
 
 	// /RES
-	void reset_w(unsigned char data = 0) { ay8910_reset_ym(chip_type == AY8930); }
+	void reset_w(unsigned char data = 0) { ay8910_reset_ym(); }
+
+	// Clock select pin
+	void set_clock_sel(bool clk_sel)
+	{
+		if (m_feature & PSG_PIN26_IS_CLKSEL)
+		{
+			if (clk_sel)
+			{
+				m_flags |= YM2149_PIN26_LOW;
+				set_type(m_type);
+			}
+			else
+			{
+				m_flags &= ~YM2149_PIN26_LOW;
+				set_type(m_type);
+			}
+		}
+	}
 
 	// use this when BC1 == A0; here, BC1=0 selects 'data' and BC1=1 selects 'latch address'
 	void data_address_w(int offset, unsigned char data) { ay8910_write_ym(~offset & 1, data); } // note that directly connecting BC1 to A0 puts data on 0 and address on 1
@@ -138,7 +156,7 @@ public:
 
 	void ay8910_write_ym(int addr, unsigned char data);
 	unsigned char ay8910_read_ym();
-	void ay8910_reset_ym(bool ay8930);
+	void ay8910_reset_ym();
 
 private:
 	static constexpr int NUM_CHANNELS = 3;
@@ -258,6 +276,18 @@ private:
 		}
 	};
 
+	inline void noise_rng_tick()
+	{
+		// The Random Number Generator of the 8910 is a 17-bit shift
+		// register. The input to the shift register is bit0 XOR bit3
+		// (bit0 is the output). This was verified on AY-3-8910 and YM2149 chips.
+
+		if (m_feature & PSG_HAS_EXPANDED_MODE) // AY8930 LFSR algorithm is slightly different, verified from manual
+			m_rng = (m_rng >> 1) | ((BIT(m_rng, 0) ^ BIT(m_rng, 2)) << 16);
+		else
+			m_rng = (m_rng >> 1) | ((BIT(m_rng, 0) ^ BIT(m_rng, 3)) << 16);
+	}
+
 	// inlines
 	inline bool tone_enable(int chan) { return BIT(m_regs[AY_ENABLE], chan); }
 	inline unsigned char tone_volume(tone_t *tone) { return tone->volume & (is_expanded_mode() ? 0x1f : 0x0f); }
@@ -267,11 +297,16 @@ private:
 
 	inline bool noise_enable(int chan) { return BIT(m_regs[AY_ENABLE], 3 + chan); }
 	inline unsigned char noise_period() { return is_expanded_mode() ? m_regs[AY_NOISEPER] & 0xff : m_regs[AY_NOISEPER] & 0x1f; }
-	inline unsigned char noise_output() { return is_expanded_mode() ? m_noise_latch & 1 : m_rng & 1; }
+	inline unsigned char noise_output() { return is_expanded_mode() ? m_noise_out & 1 : m_rng & 1; }
 
 	inline bool is_expanded_mode() { return ((m_feature & PSG_HAS_EXPANDED_MODE) && ((m_mode & 0xe) == 0xa)); }
 	inline unsigned char get_register_bank() { return is_expanded_mode() ? (m_mode & 0x1) << 4 : 0; }
 
+	inline unsigned char noise_and() { return m_regs[AY_NOISEAND] & 0xff; }
+	inline unsigned char noise_or() { return m_regs[AY_NOISEOR] & 0xff; }
+
+	inline bool is_clock_divided() { return ((m_feature & PSG_HAS_INTERNAL_DIVIDER) || ((m_feature & PSG_PIN26_IS_CLKSEL) && (m_flags & YM2149_PIN26_LOW))); }
+
 	// internal helpers
 	void set_type(psg_type_t psg_type);
 	inline float mix_3D();
@@ -284,18 +319,16 @@ private:
 	int m_ready;
 	//sound_stream *m_channel;
 	bool m_active;
-	int m_register_latch;
+	unsigned char m_register_latch;
 	unsigned char m_regs[16 * 2];
 	int m_last_enable;
 	tone_t m_tone[NUM_CHANNELS];
 	envelope_t m_envelope[NUM_CHANNELS];
 	unsigned char m_prescale_noise;
-	int m_count_noise;
+	signed short m_noise_value;
-	int m_rng;
+	signed short m_count_noise;
-  unsigned int m_noise_and;
+	unsigned int m_rng;
-  unsigned int m_noise_or;
+	unsigned char m_noise_out;
-  unsigned int m_noise_value;
-  unsigned int m_noise_latch;
 	unsigned char m_mode;
 	unsigned char m_env_step_mask;
 	/* init parameters ... */

src/gui/presets.cpp

@@ -425,6 +425,15 @@ void FurnaceGUI::initSystemPresets() {
       0
     }
   ));
+  cat.systems.push_back(FurnaceGUISysDef(
+    "MSX + Darky", {
+      DIV_SYSTEM_AY8910, 64, 0, 16,
+      DIV_SYSTEM_AY8930, 64, 0, 139, // 3.58MHz
+      DIV_SYSTEM_AY8930, 64, 0, 140, // 3.58MHz or 3.6MHz selectable via register
+      // per-channel mixer (soft panning, post processing) isn't emulated at all
+      0
+    }
+  ));
   cat.systems.push_back(FurnaceGUISysDef(
     "ZX Spectrum (48K)", {
       DIV_SYSTEM_AY8910, 64, 0, 2,

src/gui/sysConf.cpp

@@ -219,6 +219,14 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
       if (ImGui::RadioButton("2^21Hz (Game Boy)",(flags&15)==10)) {
         copyOfFlags=(flags&(~15))|10;
         
+      }
+      if (ImGui::RadioButton("3.58MHz (Darky)",(flags&15)==11)) {
+        copyOfFlags=(flags&(~15))|11;
+        
+      }
+      if (ImGui::RadioButton("3.6MHz (Darky)",(flags&15)==12)) {
+        copyOfFlags=(flags&(~15))|12;
+        
       }
       if (type==DIV_SYSTEM_AY8910) {
         ImGui::Text("Chip type:");
@@ -240,10 +248,17 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
         }
       }
       bool stereo=flags&0x40;
-      ImGui::BeginDisabled((flags&0x30)==32);
+      ImGui::BeginDisabled((type==DIV_SYSTEM_AY8910) && ((flags&0x30)==32));
       if (ImGui::Checkbox("Stereo##_AY_STEREO",&stereo)) {
         copyOfFlags=(flags&(~0x40))|(stereo?0x40:0);
         
+      }
+      ImGui::EndDisabled();
+      bool clockSel=flags&0x80;
+      ImGui::BeginDisabled((type==DIV_SYSTEM_AY8910) && ((flags&0x30)!=16));
+      if (ImGui::Checkbox("Half Clock divider##_AY_CLKSEL",&clockSel)) {
+        copyOfFlags=(flags&(~0x80))|(clockSel?0x80:0);
+        
       }
       ImGui::EndDisabled();
       break;