Make the PSG and YM2612 use the master clock internal with an increment based on clock divider so that they stay perflectly in sync. Run both the PSG and YM2612 whenver one of them needs to be run.

1 files changed, 31 insertions, 20 deletions

diff --git a/blastem.c b/blastem.c
index 559ba32..e6c6206 100644
--- a/blastem.c
+++ b/blastem.c
@@ -12,9 +12,15 @@
 #define CARTRIDGE_WORDS 0x200000
 #define RAM_WORDS 32 * 1024
 #define Z80_RAM_BYTES 8 * 1024
+
+#define MCLKS_NTSC 53693175
+#define MCLKS_PAL  53203395
+
 #define MCLKS_PER_68K 7
+#define MCLKS_PER_YM  MCLKS_PER_68K
 #define MCLKS_PER_Z80 15
 #define MCLKS_PER_PSG (MCLKS_PER_Z80*16)
+
 //TODO: Figure out the exact value for this
 #define CYCLE_NEVER 0xFFFFFFFF
 #define LINES_NTSC 262
@@ -187,6 +193,16 @@ void sync_z80(z80_context * z_context, uint32_t mclks)
 		z_context->current_cycle = mclks / MCLKS_PER_Z80;
 	}
 }
+
+void sync_sound(genesis_context * gen, uint32_t target)
+{
+	//printf("YM | Cycle: %d, bpos: %d, PSG | Cycle: %d, bpos: %d\n", gen->ym->current_cycle, gen->ym->buffer_pos, gen->psg->cycles, gen->psg->buffer_pos * 2);
+	psg_run(gen->psg, target);
+	ym_run(gen->ym, target);
+	
+	//printf("Target: %d, YM bufferpos: %d, PSG bufferpos: %d\n", target, gen->ym->buffer_pos, gen->psg->buffer_pos * 2);
+}
+
 uint32_t frame=0;
 m68k_context * sync_components(m68k_context * context, uint32_t address)
 {
@@ -197,15 +213,15 @@ m68k_context * sync_components(m68k_context * context, uint32_t address)
 	uint32_t mclks = context->current_cycle * MCLKS_PER_68K;
 	sync_z80(z_context, mclks);
 	if (mclks >= mclks_per_frame) {
-		ym_run(gen->ym, context->current_cycle);
-		gen->ym->current_cycle -= mclks_per_frame/MCLKS_PER_68K;
+		sync_sound(gen, mclks);
+		gen->ym->current_cycle -= mclks_per_frame;
+		gen->psg->cycles -= mclks_per_frame;
 		if (gen->ym->write_cycle != CYCLE_NEVER) {
 			gen->ym->write_cycle = gen->ym->write_cycle >= mclks_per_frame/MCLKS_PER_68K ? gen->ym->write_cycle - mclks_per_frame/MCLKS_PER_68K : 0;
 		}
 		//printf("reached frame end | 68K Cycles: %d, MCLK Cycles: %d\n", context->current_cycle, mclks);
 		vdp_run_context(v_context, mclks_per_frame);
-		psg_run(gen->psg, mclks/MCLKS_PER_PSG);
-		gen->psg->cycles -= mclks_per_frame/MCLKS_PER_PSG;
+		
 		if (!headless) {
 			break_on_sync |= wait_render_frame(v_context, frame_limit);
 		}
@@ -234,7 +250,7 @@ m68k_context * sync_components(m68k_context * context, uint32_t address)
 	} else {
 		//printf("running VDP for %d cycles\n", mclks - v_context->cycles);
 		vdp_run_context(v_context, mclks);
-		psg_run(gen->psg, mclks/MCLKS_PER_PSG);
+		sync_sound(gen, mclks);
 	}
 	if (context->int_ack) {
 		vdp_int_ack(v_context, context->int_ack);
@@ -326,7 +342,7 @@ m68k_context * vdp_port_write(uint32_t vdp_port, m68k_context * context, uint16_
 		}
 	} else if (vdp_port < 0x18) {
 		genesis_context * gen = context->system;
-		psg_run(gen->psg, (context->current_cycle * MCLKS_PER_68K) / MCLKS_PER_PSG);
+		sync_sound(gen, context->current_cycle * MCLKS_PER_68K);
 		psg_write(gen->psg, value);
 	} else {
 		//TODO: Implement undocumented test register(s)
@@ -358,7 +374,7 @@ z80_context * z80_vdp_port_write(uint16_t vdp_port, z80_context * context, uint8
 			exit(1);
 		}
 	} else if (vdp_port < 0x18) {
-		psg_run(gen->psg, (context->current_cycle * MCLKS_PER_Z80) / MCLKS_PER_PSG);
+		sync_sound(gen, context->current_cycle * MCLKS_PER_Z80);
 		psg_write(gen->psg, value);
 	} else {
 		//TODO: Implement undocumented test register(s)
@@ -494,7 +510,7 @@ m68k_context * io_write(uint32_t location, m68k_context * context, uint8_t value
 				z80_ram[location & 0x1FFF] = value;
 				z80_handle_code_write(location & 0x1FFF, gen->z80);
 			} else if (location < 0x6000) {
-				ym_run(gen->ym, context->current_cycle);
+				sync_sound(gen, context->current_cycle * MCLKS_PER_68K);
 				if (location & 1) {
 					ym_data_write(gen->ym, value);
 				} else if(location & 2) {
@@ -594,7 +610,7 @@ m68k_context * io_write_w(uint32_t location, m68k_context * context, uint16_t va
 				z80_ram[location & 0x1FFE] = value >> 8;
 				z80_handle_code_write(location & 0x1FFE, gen->z80);
 			} else if (location < 0x6000) {
-				ym_run(gen->ym, context->current_cycle);
+				sync_sound(gen, context->current_cycle * MCLKS_PER_68K);
 				if (location & 1) {
 					ym_data_write(gen->ym, value >> 8);
 				} else if(location & 2) {
@@ -700,7 +716,7 @@ uint8_t io_read(uint32_t location, m68k_context * context)
 			if (location < 0x4000) {
 				value = z80_ram[location & 0x1FFF];
 			} else if (location < 0x6000) {
-				ym_run(gen->ym, context->current_cycle);
+				sync_sound(gen, context->current_cycle * MCLKS_PER_68K);
 				value = ym_read_status(gen->ym);
 			} else {
 				value = 0xFF;
@@ -767,7 +783,7 @@ uint16_t io_read_w(uint32_t location, m68k_context * context)
 			if (location < 0x4000) {
 				value = z80_ram[location & 0x1FFE];
 			} else if (location < 0x6000) {
-				ym_run(gen->ym, context->current_cycle);
+				sync_sound(gen, context->current_cycle * MCLKS_PER_68K);
 				value = ym_read_status(gen->ym);	
 			} else {
 				value = 0xFF;
@@ -830,7 +846,7 @@ uint16_t io_read_w(uint32_t location, m68k_context * context)
 z80_context * z80_write_ym(uint16_t location, z80_context * context, uint8_t value)
 {
 	genesis_context * gen = context->system;
-	ym_run(gen->ym, (context->current_cycle * MCLKS_PER_Z80) / MCLKS_PER_68K);
+	sync_sound(gen, context->current_cycle * MCLKS_PER_Z80);
 	if (location & 1) {
 		ym_data_write(gen->ym, value);
 	} else if (location & 2) {
@@ -844,7 +860,7 @@ z80_context * z80_write_ym(uint16_t location, z80_context * context, uint8_t val
 uint8_t z80_read_ym(uint16_t location, z80_context * context)
 {
 	genesis_context * gen = context->system;
-	ym_run(gen->ym, (context->current_cycle * MCLKS_PER_Z80) / MCLKS_PER_68K);
+	sync_sound(gen, context->current_cycle * MCLKS_PER_Z80);
 	return ym_read_status(gen->ym);
 }
 
@@ -1810,11 +1826,6 @@ void detect_region()
 	}
 }
 
-#define PSG_CLKS_NTSC (3579545/16)
-#define PSG_CLKS_PAL (3546893/16)
-#define YM_CLKS_NTSC 7670454
-#define YM_CLKS_PAL 7600485
-
 int main(int argc, char ** argv)
 {
 	if (argc < 2) {
@@ -1899,10 +1910,10 @@ int main(int argc, char ** argv)
 	init_vdp_context(&v_context);
 	
 	ym2612_context y_context;
-	ym_init(&y_context, render_sample_rate(), fps == 60 ? YM_CLKS_NTSC : YM_CLKS_PAL, render_audio_buffer());
+	ym_init(&y_context, render_sample_rate(), fps == 60 ? MCLKS_NTSC : MCLKS_PAL, MCLKS_PER_YM, render_audio_buffer());
 	
 	psg_context p_context;
-	psg_init(&p_context, render_sample_rate(), fps == 60 ? PSG_CLKS_NTSC : PSG_CLKS_PAL, render_audio_buffer());
+	psg_init(&p_context, render_sample_rate(), fps == 60 ? MCLKS_NTSC : MCLKS_PAL, MCLKS_PER_PSG, render_audio_buffer());
 	
 	z80_context z_context;
 	x86_z80_options z_opts;