On Tue, Jan 14, 2003 at 07:54:06AM -0800, Jason R Thorpe wrote:
> On Tue, Jan 14, 2003 at 04:37:58PM +0100, Mipam wrote:
> 
>  > onboard stuff (ie ide controller and onboard lan controller (if its
>  > onboard anyway)) is connected by the pcibus anyway, so it doesnt really
>  > matter whether you got onboard stuff or not concerning the speed.
>  > Is this still true that most of the onboard stuff (ide controller, scsi
>  > controller, lan controller, audio (if onboard)) if connected to the pci
>  > bus anyway?
> 
> Correct, on PCs, any high-speed peripherals that are on-board are going
> to be connected to PCI anyay.

Some modern PC chipsets do use a fast bus between the north bridge
(memory controller) and south bridge (peripheral controller) with
the PCI bus coming of the south bridge.  In this case the disks
connected to the south bridge are not limited by the PCI bus.

ISTR A 66MHz PCI bus gets downgraded to 33MHz if you connect any 33MHz
cards to it.

>  > Or an smp machine with a pci bus for each processor would be even more
>  > convenient then? Any suggestions towards this and perhaps some hints for
>  > reading on this?
> 
> You're not likely to find a "PCI bus for each processor" because such
> a configuration wouldn't really help anything -- you're not likely to
> have a set of disks for each processor, for example.

OTOH you might find a server motherboard that has 2 PCI busses that
are both bridged off the main system bus - rather than from each other.

Another possibility (eg some sparc systems) is to have a 66MHz PCI
bus from the processor module that is bridged to two separate 33MHz
PCI busses.  This allows both 33MHz busses to be used to near
capacity.

	David

-- 
David Laight: david@l8s.co.uk