Re: Going beyond 256 PCI buses

Jonathan Lundell
2001-06-14T20:51:49Z

At 12:03 PM -0700 2001-06-14, David S. Miller wrote:
>Jonathan Lundell writes:
> > As I recall, even a midline chipset such as the ServerWorks LE
> > supports the use of two north bridges, which implies two PCI bus
> > domains.
>
>It hides this fact by making config space accesses respond in such a
>way that it appears that it is all behind one PCI controller. The
>BIOS even avoids allowing any of the MEM and I/O resources from
>overlapping.

So we end up with a single domain and max 256 buses. Still, it's not
behavior one can count on. Sun's U2P PCI controller certainly creates
a new PCI domain for each controller. It's easier in architectures
other than IA32, in a way, since they typically don't have the 64KB
IO-space addressing limitation that makes heavily bridged systems
problematical on IA32 (one tends to run out of IO space).
--
/Jonathan Lundell.