On Tue, Oct 26, 2004 at 10:00:32AM +0200, Erik C.J. Laan wrote:
One area I think Linux/mac68k is lacking is SCSI DMA support on the
NCR53c9x. This makes these machines quite slow. If you can help out with
that is would be great, although the Linux/mac68k status page tells me
your PB540c has a NCR5380. Someone did write (some parts?) of the
SCSI-DMA driver for that.
Actually, only a few models have a real DMA engine. The AV models have
the PSC doing DMA for the NCR53c94 chip, which has been partially
documented, but not coded. The IIfx has a custom version of the NCR5380
with a DMA engine, but I couldn't get the driver stabilized. I haven't
tried with the 2.6 code yet, because it doesn't even work in PIO mode
on my IIfx in recent versions. I have the docs laying around for SCSI-DMA
on the IIfx, but I don't think they're 100% accurate.
All other models have to use either PIO or PDMA. The mac_scsi driver
implemented PDMA for most models with the NCR5380, but I don't remember
anyone updating the mac_esp driver to get PDMA on NCR53c9x based models.