ISA DMA take 2

Adrian Cox adrian at
Thu Jan 10 04:40:33 EST 2002

Michael Sokolov wrote:

> What's your memory map? Do you put the bottom 16 MB of main memory in the
> bottom 16 MB of the PCI memory space on the PCI segment with the Via without an
> I/O hole?

Yes - and I set ISA_DMA_THRESHOLD to 0x00ffffff. It's not possible to
use ISA DMA with the Via southbridge unless you have main memory at 0x0
on the PCI bus.

Of course, if anybody knows a cheap southbridge with 32-bit ISA DMA,
UDMA100, and maybe USB, it would be nice to hear of it for future boards.

Adrian Cox

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