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core, improve 68k timing accuracy

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This commit is contained in:
kub 2023-07-11 21:18:05 +00:00
parent a5aae2c39f
commit 7263343dc7
8 changed files with 76 additions and 63 deletions
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27
pico/cd/mcd.c
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@ -123,18 +123,13 @@ static void SekRunS68k(unsigned int to)
pprof_end(s68k);
}
static void pcd_set_cycle_mult(void)
void PicoMCDPrepare(void)
{
unsigned int div;
if (Pico.m.pal)
div = 50*313*488;
else
div = 60*262*488;
// ~1.63 for NTSC, ~1.645 for PAL; round to nearest, x/y+0.5 -> (x+y/2)/y
mcd_m68k_cycle_mult = ((12500000ull << 16) + div/2) / div;
mcd_s68k_cycle_mult = ((1ull*div << 16) + 6250000) / 12500000;
// ~1.63 for NTSC, ~1.645 for PAL
#define DIV_ROUND(x,y) ((x)+(y)/2) / (y) // round to nearest, x/y+0.5 -> (x+y/2)/y
unsigned int osc = (Pico.m.pal ? OSC_PAL : OSC_NTSC);
mcd_m68k_cycle_mult = DIV_ROUND(12500000ull << 16, osc / 7);
mcd_s68k_cycle_mult = DIV_ROUND(1ull * osc << 16, 7 * 12500000);
}
unsigned int pcd_cycles_m68k_to_s68k(unsigned int c)
@ -312,11 +307,13 @@ int pcd_sync_s68k(unsigned int m68k_target, int m68k_poll_sync)
#define pcd_run_cpus_normal pcd_run_cpus
//#define pcd_run_cpus_lockstep pcd_run_cpus
static void SekAimM68k(int cyc, int mult);
static int SekSyncM68k(int once);
void pcd_run_cpus_normal(int m68k_cycles)
{
Pico.t.m68c_aim += m68k_cycles;
// TODO this is suspicious. ~1 cycle refresh delay every 256 cycles?
SekAimM68k(m68k_cycles, 0x43); // Fhey area
while (CYCLES_GT(Pico.t.m68c_aim, Pico.t.m68c_cnt)) {
if (SekShouldInterrupt()) {
@ -376,8 +373,6 @@ void pcd_run_cpus_lockstep(int m68k_cycles)
void pcd_prepare_frame(void)
{
pcd_set_cycle_mult();
// need this because we can't have direct mapping between
// master<->slave cycle counters because of overflows
mcd_m68k_cycle_base = Pico.t.m68c_aim;
@ -397,7 +392,6 @@ void pcd_state_loaded(void)
unsigned int cycles;
int diff;
pcd_set_cycle_mult();
pcd_state_loaded_mem();
memset(Pico_mcd->pcm_mixbuf, 0, sizeof(Pico_mcd->pcm_mixbuf));
@ -407,8 +401,7 @@ void pcd_state_loaded(void)
// old savestates..
cycles = pcd_cycles_m68k_to_s68k(Pico.t.m68c_aim);
diff = cycles - SekCycleAimS68k;
if (diff < -1000 || diff > 1000) {
if (CYCLES_GE(cycles - SekCycleAimS68k, 1000)) {
SekCycleCntS68k = SekCycleAimS68k = cycles;
}
if (pcd_event_times[PCD_EVENT_CDC] == 0) {