On Mon, 1 Nov 1999 mcr@solidum.com wrote:

>   Does anyone know much about how the 64 bit host bridges deals with
> running 32-bit operating systems with 64 bit PCI buses? Does the PIII have
> 64-bit address modes? Should NetBSD running on such a system be considered to
> be a completely different kernel architecture a la sparc vs sparc64?

There's a difference between a 64-bit address space in PCI and a 64-bit
data path. I don't think that the PIII has 64-bit address modes (the name
ia32 says a lot :-) . As long as it's using a 32-but address space, 32-bit
OS's are fine. The 64-bit data path will just speed up i/o.

>   Should we consider buying Alpha or Sparc PCI motherboards instead of
> Pentium if we want 64 bit PCI buses?  We are building some peripherals that
> would like to have 2^31 blocks of PCI addresses, as well as the bandwidth of
> 64-bit PCI.

If you really need 2^31 byte blocks of PCI addresses, you need a bigger
processer architecture. I think either alpha or sparc64 would work, but
alpha is a bit more mature. Any NetBSD port should be able to handle the
bandwith advantage of 64-bit PCI, though.

Take care,

Bill