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Revision 1 CPU DMA crash

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Little is known about why the CPU revision 1 DMA crash happens. In 2015, Ramsis wrote a test rom to trigger it. [2]

Trigger

kicking of an HDMA at about the same time that a General Purpose DMA finishes

Symptoms

Sometimes the 5A22 will crash
Sometimes the HDMA will not happen correctly

Workarounds

Use GPDMA only during vblank
Make sure HDMA starts in the middle of a GPDMA data transfer
Avoid HDMA
Adjust the time at which GPDMA begins
Decrease the number of bytes transferred during GPDMA

References

page 2-25-1 of Book I of the official Super Nintendo development manual
https://forums.nesdev.org/viewtopic.php?t=13280

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