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| author | user <user@clank> | 2026-07-18 22:06:35 +0200 |
|---|---|---|
| committer | user <user@clank> | 2026-07-18 22:06:35 +0200 |
| commit | 4425150cb6f52d15f513690a75645639358a2030 (patch) | |
| tree | b186e048c286f7fb9b78552fb10ebf417ac5178c /src/syscall.asm | |
| parent | term: latch SCY in VBlank - fix ring-scroll shear on live displays (diff) | |
| download | gbos-4425150cb6f52d15f513690a75645639358a2030.tar.gz gbos-4425150cb6f52d15f513690a75645639358a2030.tar.xz gbos-4425150cb6f52d15f513690a75645639358a2030.zip | |
kernel: CGB double-speed mode - 2x everything (1.99x measured)
KEY1 prepare + STOP at KernelInit (skipped on warm reboot if already
fast). The PPU/LCD keep their normal rate; the timer and DIV double
with the CPU, compensated at the two consumers:
- TimerISR now fires at 128 Hz; a toggle byte keeps wTicks at 64 Hz
(uptime semantics unchanged)
- sys_sleep halves the DIV-delta accumulator's high byte (256 DIV
ticks = 1/128 s in double speed) so gsleep/msleep stay real-time
Measured: count 60 (scroll-heavy) 3.77s -> 1.89s wall; wTicks 64 Hz
over 4s; ping's 800ms msleep pacing unchanged (2.77s for 4 echoes).
sl0pboy already emulated KEY1/STOP + per-speed timer/PPU rates.
Diffstat (limited to 'src/syscall.asm')
| -rw-r--r-- | src/syscall.asm | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/syscall.asm b/src/syscall.asm index e3f0b1b..4bcb601 100644 --- a/src/syscall.asm +++ b/src/syscall.asm @@ -277,8 +277,10 @@ ENDR ; ----------------------------------------------------------------------------- ; sys_sleep(B = 1/64-second units) - cooperative delay driven by the DIV timer. -; DIV (FF04) free-runs at 16384 Hz, so 256 ticks = 1/64 s. We accumulate DIV -; deltas across SchedYields (other procs run) until enough units have elapsed. +; DIV free-runs at 16384 Hz - 32768 Hz in double-speed mode, where 256 ticks +; = 1/128 s - so the accumulated high byte is halved before comparing against +; the target. We accumulate DIV deltas across SchedYields (other procs run) +; until enough 1/64-second units have elapsed. ; ----------------------------------------------------------------------------- sys_sleep: ld a, b @@ -305,7 +307,8 @@ sys_sleep: ld [wSleepAcc], a ld a, [wSleepAcc+1] adc 0 - ld [wSleepAcc+1], a ; acc high byte = elapsed 1/64-second units + ld [wSleepAcc+1], a ; acc high byte = elapsed 1/128-second units + srl a ; /2: double-speed DIV -> 1/64-second units ld b, a ld a, [wSleepTarget] cp b |