Switch to 2MHz units in apu_cycles

Core/apu.c

@@ -633,9 +633,11 @@ static void step_lfsr(GB_gameboy_t *gb, unsigned cycles_offset)
 
 void GB_apu_run(GB_gameboy_t *gb, bool force)
 {
-    uint32_t clock_rate = GB_get_clock_rate(gb) * 2;
+    uint32_t clock_rate = GB_get_clock_rate(gb) * 2;    
+    uint16_t cycles = gb->apu.apu_cycles;
+
     if (force ||
-        (gb->apu.apu_cycles > 0x1000) ||
+        (gb->apu.apu_cycles > 0x400) ||
         (gb->apu_output.sample_cycles >= clock_rate) ||
         (gb->apu.square_sweep_calculate_countdown || gb->apu.channel_1_restart_hold || gb->apu.square_sweep_calculate_countdown_reload_timer) ||
         (gb->model <= GB_MODEL_CGB_E && (gb->apu.wave_channel.bugged_read_countdown || (gb->apu.wave_channel.enable && gb->apu.wave_channel.pulsed)))) {
@@ -644,8 +646,7 @@ void GB_apu_run(GB_gameboy_t *gb, bool force)
     if (!force) {
         return;
     }
-    /* Convert 4MHZ to 2MHz. apu_cycles is always divisable by 4. */
+
-    uint16_t cycles = gb->apu.apu_cycles >> 2;
     gb->apu.apu_cycles = 0;
     if (!cycles) return;
     
@@ -677,7 +678,7 @@ void GB_apu_run(GB_gameboy_t *gb, bool force)
             else {
                 /* Split it into two */
                 cycles -= gb->apu.noise_channel.dmg_delayed_start;
-                gb->apu.apu_cycles = gb->apu.noise_channel.dmg_delayed_start * 4;
+                gb->apu.apu_cycles = gb->apu.noise_channel.dmg_delayed_start;
                 GB_apu_run(gb, true);
             }
         }
@@ -854,6 +855,7 @@ void GB_apu_run(GB_gameboy_t *gb, bool force)
 void GB_apu_init(GB_gameboy_t *gb)
 {
     memset(&gb->apu, 0, sizeof(gb->apu));
+    gb->apu.apu_cycles_in_2mhz = true;
     gb->apu.lf_div = 1;
     gb->apu.wave_channel.shift = 4;
     /* APU glitch: When turning the APU on while DIV's bit 4 (or 5 in double speed mode) is on,
@@ -1154,6 +1156,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
                 memset(&gb->apu, 0, sizeof(gb->apu));
                 memset(gb->io_registers + GB_IO_NR10, 0, GB_IO_WAV_START - GB_IO_NR10);
                 gb->apu.global_enable = false;
+                gb->apu.apu_cycles_in_2mhz = true;
             }
 
             if (!GB_is_cgb(gb) && (value & 0x80)) {
@@ -1627,7 +1630,6 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
 
 void GB_set_sample_rate(GB_gameboy_t *gb, unsigned sample_rate)
 {
-
     gb->apu_output.sample_rate = sample_rate;
     if (sample_rate) {
         gb->apu_output.highpass_rate = pow(0.999958,  GB_get_clock_rate(gb) / (double)sample_rate);

Core/apu.h

@@ -148,6 +148,8 @@ typedef struct
         GB_SKIP_DIV_EVENT_SKIP,
     }) skip_div_event;
     uint8_t pcm_mask[2]; // For CGB-0 to CGB-C PCM read glitch
+    
+    bool apu_cycles_in_2mhz; // For compatibility with 0.16.x save states
 } GB_apu_t;
 
 typedef enum {

Core/gb.c

@@ -1787,6 +1787,7 @@ static void GB_reset_internal(GB_gameboy_t *gb, bool quick)
         gb->io_registers[GB_IO_OBP0] = preserved_state->obp0;
         gb->io_registers[GB_IO_OBP1] = preserved_state->obp1;
     }
+    gb->apu.apu_cycles_in_2mhz = true;
     
     gb->magic = GB_state_magic();
     request_boot_rom(gb);
@@ -1905,8 +1906,10 @@ GB_registers_t *GB_get_registers(GB_gameboy_t *gb)
 
 void GB_set_clock_multiplier(GB_gameboy_t *gb, double multiplier)
 {
-    gb->clock_multiplier = multiplier;
+    if (multiplier != gb->clock_multiplier) {
-    GB_update_clock_rate(gb);
+        gb->clock_multiplier = multiplier;
+        GB_update_clock_rate(gb);
+    }
 }
 
 uint32_t GB_get_clock_rate(GB_gameboy_t *gb)
@@ -1932,6 +1935,7 @@ void GB_update_clock_rate(GB_gameboy_t *gb)
     }
     
     gb->clock_rate = gb->unmultiplied_clock_rate * gb->clock_multiplier;
+    GB_set_sample_rate(gb, gb->apu_output.sample_rate);
 }
 
 void GB_set_border_mode(GB_gameboy_t *gb, GB_border_mode_t border_mode)

Core/save_state.c

@@ -425,6 +425,11 @@ static void sanitize_state(GB_gameboy_t *gb)
     if (gb->camera_update_request_callback) {
         GB_camera_updated(gb);
     }
+    
+    if (!gb->apu.apu_cycles_in_2mhz) {
+        gb->apu.apu_cycles >>= 2;
+        gb->apu.apu_cycles_in_2mhz = true;
+    }
 }
 
 static bool dump_section(virtual_file_t *file, const void *src, uint32_t size)

Core/timing.c

@@ -252,7 +252,7 @@ static void timers_run(GB_gameboy_t *gb, uint8_t cycles)
 {
     if (gb->stopped) {
         if (GB_is_cgb(gb)) {
-            gb->apu.apu_cycles += 4 << !gb->cgb_double_speed;
+            gb->apu.apu_cycles += 1 << !gb->cgb_double_speed;
         }
         return;
     }
@@ -266,7 +266,7 @@ static void timers_run(GB_gameboy_t *gb, uint8_t cycles)
     while (true) {
         advance_tima_state_machine(gb);
         GB_set_internal_div_counter(gb, gb->div_counter + 4);
-        gb->apu.apu_cycles += 4 << !gb->cgb_double_speed;
+        gb->apu.apu_cycles += 1 << !gb->cgb_double_speed;
         GB_SLEEP(gb, div, 2, 4);
     }
 }