> On Wed, Nov 28, 2001 at 09:54:23AM -0600, Mike Hicks wrote:
> > That's cool.. Anyone know of PC motherboards that split off and have
> > several PCI buses? It'd be great to stick slower devices on one bus (ISA
> > bus, USB, etc), then faster bits on another (Ethernet, FireWire, IDE
> > and/or SCSI). I guess Apple does something like this on some of their
> > machines (my brother's PowerBook, at least).
> >
> > Then again, maybe there isn't much of an advantage to that..
>
> I just put together an ABIT KT7A-based system last night and, based on
> (my memory of) the system diagrams in the manual, it appears to have
> something similar to what you describe with one bus (the "north bridge")
> handling PCI cards and a separate bus ("south bridge") for the single
> ISA slot, PS/2 connector, keyboard, etc.
yeah, it's normal to split the PCI and ISA buses apart; since they're
completely different architectures.
multiple PCI buses on x86 machines are common on the really big servers
(quads and octuples); they need to be. there's only so many PCI devices you
can put on a bus, and only so much bandwidth you can get out of it. I think
the Compaq 8-ways have 3 PCI busses; but don't quote me on that.
as I understand it, 64-bit PCI devices are limited to only 2 per bus
(something to do with impedance problems, tho I don't remember clearly). so
if a machine has more than 2 64-bit PCI slots; it needs multiple busses, or
else only 2 of them will be usable at a time.
Carl Soderstrom.
--
Network Engineer
Real-Time Enterprises
(952) 943-8700