Notes about the DMG wave-ram glitch
@@ -691,8 +691,13 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.wave_channel.enable) {
unsigned offset = ((gb->apu.wave_channel.current_sample_index + 1) >> 1) & 0xF;
- /* On SGB2 (and probably SGB1 and MGB as well) this behavior is not accurate,
- however these systems are not currently emulated. */
+ /* This glitch varies between models and even specific instances:
+ DMG-B: Most of them behave as emulated. A few behave differently.
+ SGB: As far as I know, all tested instances behave as emulated.
+ MGB, SGB2: Most instances behave non-deterministically, a few behave as emulated.
+
+ Additionally, I believe DMGs, including those we behave differently than emulated,
+ are all deterministic. */
if (offset < 4) {
gb->io_registers[GB_IO_WAV_START] = gb->io_registers[GB_IO_WAV_START + offset];
gb->apu.wave_channel.wave_form[0] = gb->apu.wave_channel.wave_form[offset / 2];
