Charlie<charlieDOTd@verEYEzon.net> wrote:
On 5/7/2011 12:52 AM, David Empson wrote:
[Details about DMA usage patterns in Apple II cards]
Thanks for the detailed information. It looks like I've been lucky so
far as it seems that the Carte Blanche is using DMA in the background
and worse it's in slot #1 and the HS SCSI is in slot #7 with three of
the slots between them empty. After reading your post, I switched the
DMA off on my HS SCSI card until I can get rid of the Z80/DMA stuff on
the Carte Blanche card. I also have a Zip GSX card. Does it use DMA?
The Zip GSX is fine. Its CPU replaces the main CPU, and the card doesn't
do DMA itself. It correctly responds to DMA control signals to disable
the CPU while an I/O card wants to do a DMA transfer. The same applies
to the TransWarp GS.
For 8-bit Apple IIs, most accelerators are not compatible with I/O cards
which use DMA. At a miminum, the accelerator must have access to the
slot signals as well as the CPU socket (so the Zip Chip and Rocket Chip
cannot be DMA compatible), but even some accelerators which plug into
both the slot and CPU socket are not compatible with DMA.