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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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28
pico/pico_cmn.c
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@ -66,15 +66,22 @@ static int SekSyncM68k(int once)
return Pico.t.m68c_aim > Pico.t.m68c_cnt;
}
static __inline void SekAimM68k(int cyc, int mult)
{
// refresh slowdown, for cart: 2 cycles every 128 - make this 1 every 64,
// for RAM: seems to be 0-3 every 128. Carts usually run from the cart
// area, but MCD games only use RAM, hence a different multiplier is needed.
// NB must be quite accurate, so handle fractions as well (c/f OutRunners)
int delay = (Pico.t.refresh_delay += cyc*mult) >> 14;
Pico.t.m68c_cnt += delay;
Pico.t.refresh_delay -= delay << 14;
Pico.t.m68c_aim += cyc;
}
static __inline void SekRunM68k(int cyc)
{
// refresh slowdown handling, 2 cycles every 128 - make this 1 every 64
// NB must be quite accurate, so handle fractions as well (c/f OutRunners)
static int refresh;
Pico.t.m68c_cnt += (cyc + refresh) >> 6;
refresh = (cyc + refresh) & 0x3f;
Pico.t.m68c_aim += cyc;
// TODO 0x100 would by 2 cycles/128, moreover far too sensitive
SekAimM68k(cyc, 0x10c); // OutRunners, testpico, VDPFIFOTesting
SekSyncM68k(0);
}
@ -108,10 +115,9 @@ static void do_timing_hacks_end(struct PicoVideo *pv)
PicoVideoFIFOSync(CYCLES_M68K_LINE);
// need rather tight Z80 sync for emulation of main bus cycle stealing
if (Pico.m.scanline&1) {
if (Pico.m.scanline&1)
if (Pico.m.z80Run && !Pico.m.z80_reset && (PicoIn.opt&POPT_EN_Z80))
PicoSyncZ80(Pico.t.m68c_aim);
}
}
static void do_timing_hacks_start(struct PicoVideo *pv)
@ -122,6 +128,8 @@ static void do_timing_hacks_start(struct PicoVideo *pv)
// XXX how to handle Z80 bus cycle stealing during DMA correctly?
if ((Pico.t.z80_buscycles -= cycles) < 0)
Pico.t.z80_buscycles = 0;
if (Pico.m.scanline&1)
Pico.t.m68c_aim += 1; // add cycle each other line for 488.5 cycles/line
}
static int PicoFrameHints(void)
@ -167,7 +175,7 @@ static int PicoFrameHints(void)
}
// decide if we draw this line
if (!skip && (PicoIn.opt & POPT_ALT_RENDERER))
if ((PicoIn.opt & POPT_ALT_RENDERER) && !skip)
{
// find the right moment for frame renderer, when display is no longer blanked
if ((pv->reg[1]&0x40) || y > 100) {