On Fri, Oct 29, 2004 at 04:46:50PM +0200, Erik C.J. Laan wrote:
Ah, that's it, sorry I wasn't specific enough. I meant PDMA (Pseudo-DMA
right?). This makes the 5380 based Mac's much more enjoyable compared to
the 53c9x based ones. At least that is what I've been told by happy
owners of 5380 based machines when PDMA was introduced...
Yes, that's true. However, not all 5380 models have support in the
current driver. In particular, I know the IIfx is still restricted
to PIO mode. The real DMA engine gets in the way and requires some
extra code to disable it that isn't needed in PIO mode.
At this moment my 53c9x based Mac (Quadra650) is doing another testrun
with the new debian-installer. This takes me about 8 to 16 hours. This
is partly due to having little memory (only 24 Mb), and partly due to
the slowness of the SCSI-driver. If PDMA can speed this up it would save
everybody quite some time with al their Linux/Mac68k related work.
It would help quite a bit, but someone would have to take the time
to figure out how it works. I seem to recall that the 5380 support
was reverse-engineered out of the official Apple driver. I've got
other things higher on my list, but maybe someone else will find the
time to fix it. If someone needs to know how it works in mac_scsi.c,
I think I figured it out enough to explain it.