Re: Going beyond 256 PCI buses

[Jonathan Lundell]

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.