Were you actually using 64-bit addresses on the PCI bus?
My guess is that with some creative address mappings, this could be
done. The PCI bus itself would use only 32-bit address, but the CPU
would use a base address offset into the >4G range.
Yeah, I could see how that could get ugly...
Matthew D. Dharm Senior Software Designer
Momentum Computer Inc. 1815 Aston Ave. Suite 107
(760) 431-8663 X-115 Carlsbad, CA 92008-7310
Momentum Works For You www.momenco.com
> -----Original Message-----
> From: firstname.lastname@example.org
> [mailto:email@example.com]On Behalf Of Jason Gunthorpe
> Sent: Monday, January 14, 2002 4:00 PM
> To: Matthew Dharm
> Cc: firstname.lastname@example.org
> Subject: RE: MIPS64 status?
> On Mon, 14 Jan 2002, Matthew Dharm wrote:
> > Does this mean we could map PCI memory/IO addresses above
> 4G and have
> > it work?
> Ooh, don't go there :> We looked at that and actually did
> it then backed
> it out.
> The PCI spec (particuarly PCI-X) tries to make it possible, but in a
> general system with PCI sockets/etc it is just is not feasible. PCI
> bridges need to be located below 4G, as do the majority of
> devices made.
> There is also a performance hit for having device registers > 4G.
> You'd definately need the mips64 kernel to do that, or use
> ugly wired TLB
> entries with normal mips.