Subject: Re: Oooooh... IDE to Q-bus/Unibus adapters.
To: None <port-vax@netBSD.org>
From: Allison J Parent <email@example.com>
Date: 07/07/1999 23:15:43
<...but also remember that you're looking at PCI IDE chips! I don't know
Why would I look at them? they are awkward to use on a 16bit bus and the
IDE interface for PIO requires very little. Qbus DMA is pretty simple
if you limit it to single transacion and no list linkages.
I didn't bring PCI and their chips into this discussion. Look at the
Ukraine design for how simple it can be with PIO alone.
<products which use a "standard" IDE interface but which also support
<DMA ... they supply the DMA engine that merely does the PIO to the chip
Contradiction of terms. PIO is cpu doing the work, the 8237 pcstyle DMA
is not a cpu but a simple get/put DMA.
<Also, AFAIK, every VAXstation that has a SCSI chip has the capability
<of doing DMA to/from that SCSI chip. It is merely an issue of the NetBSD
<driver for that SCSI chip not supporting DMA.
Yep!. Reason, apparently a lack of documentation on the DMA system
and it's interactions with the brain hampers NCR chip.