Re: WIndowsNT "snoop" cycles before doing DMA

["Jeff" <jmd@audio2.engr.sgi.com>]

> OK, this is a question which more related to WindowsNT and not to PCI.
> Sorry for this. But perhaps somebody can help us because these
> "snooping" RW cycles
> produce a performance reduction and leads to a large RW activity (mix
> of DMA cycles and
> "snooping" RW cycles on the PCI bus) with a lot of side effects.

This touches on a Microsoft question I have had for some time
about PCI peer-to-peer DMA. Microsoft, has stated that they
wil _not_ support PCI peer-to-peer DMA. Unfortunately, They
don't say why, does anybody know? My guess is that it has
to do with coherency issues, but I would like to here it
from somebody that knows, any Microsoft people on this list?


Jeff