> AFAIK, the only 68k Macs that do SCSI by DMA are the IIfx and the AV
> machines (Allen, Scott?).

This is correct.  The mac has "DMA" only in that all devices are memory
mapped and nubus cards can access main memory directly.  The only macs
that have DMA controllers that can drive devices independently are
SCSI/DMA nubus cards (ATTO?, Jackhammer?, AWS95 PDS card?) and the IIfx
(DMA used only by A/UX) and the AV machines--which really needs SCSI
Manager 4.3 to make use of the DMA SCSI, I think.  I don't know how much
the DMA engine has changed in the powermacs, but I doubt that it's
changed too much from the AV machines.

> All others do some kind of pseudo-DMA where the CPU monitors the
> ncr53c{80,96}'s DMA handshake lines.

Correct, except I don't think that's true for the 53c9x.  At least, I
haven't yet figured out how it would work...

-allen

-- 
              Allen Briggs - end killing - briggs@macbsd.com