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Re: newbie questions for amd64

On Mon, Nov 17, 2003 at 05:09:09PM -0600, Marcelo E. Magallon wrote:

 >  If you look at the spec, nothing really speaks against a system with
 >  multiple AGP bridges, but it's so vertical that I don't think anyone
 >  has bothered to produce one.  Interestingly an n-way Opteron should be
 >  able to cope with this, but the motherboards don't support that config.

In an Opteron system, you must keep all the on-CPU northbridges coherent.
So even though you have a GART per CPU, they all have to have the same

 >  From the look of it, even the kernel supports this, but I asked Dave
 >  Jones if there was a reason for that (meaning, is it because it can be
 >  done or because there's a box in a basement somewhere where this
 >  actually exists) but he never came back to me.

Apologies for that, I've no recollection of that mail, so either spamassassin
ate it, or it got lost somewhere.
 > There's a company (big
 >  name, I'm not sure if I can really mention it, sorry) which considered
 >  putting out a system with support for multiple AGP devices

SGI still seem to be very interested in Linux supporting multiple AGP bridges.
The 2.6 code is most of the way there, most of the routines that care
now take a ptr to a bridge structure instead of using one global struct.
The lack of hardware to test this stuff on means it may still be missing
some smarts however. Whether or not that changes in the future depends on
how interested certain vendors are in Linux supporting it out of the box.
Given the hardware they're talking about it very specialised however,
and they're not adverse to putting out their own clone of a certain distro,
I'm doubtful it'll ever go to mainline. Time will tell.


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