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amiga/paulafdc.cpp: stabilize wordsync

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angelosa 2025-01-14 14:44:27 +01:00
parent 7907866577
commit 96736e433e
1 changed files with 6 additions and 8 deletions
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14
src/mame/amiga/paulafdc.cpp
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@ -7,13 +7,6 @@
Contained inside MOS 8364 Paula device
TODO:
- Some games currently writes 2+ dsksync to the buffer (marked as "[FDC] dsksync" in SW list):
Current workaround:
1. comment out dma_write in DMA_WAIT_START handling and change the dma_state *only*;
2. remove all of the non-DMA_WAIT_START phase inside the dsksync sub-section;
NB: according to documentation syncing doesn't really write anything on the bus,
so technically this "workaround" is more correct.
However it unfortunately causes other SW regressions, most notably in Workbench.
- Other games trashes memory or refuses to boot, in a few instances randomly
(marked as "[FDC] with adkcon=1100", implies dsksync disabled):
they often uses the AmigaDOS trackdisk BIOS functions, which may be expecting a
@ -281,7 +274,6 @@ void paula_fdc_device::live_run(const attotime &limit)
if(!(dskbyt & 0x2000)) {
if(cur_live.shift_reg == dsksync) {
if(adkcon & 0x0400) {
// FIXME: exact dsksync behaviour, cfr. note at top
if(dma_state == DMA_WAIT_START) {
cur_live.bit_counter = 0;
@ -290,6 +282,12 @@ void paula_fdc_device::live_run(const attotime &limit)
else
dma_done();
}
else if (dma_state != DMA_IDLE)
{
// assume wordsync (12) and DMA byte ready (15) mutually exclusive
dma_write(dsksync);
cur_live.bit_counter = 0;
}
}
dskbyt |= 0x1000;