> 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