[coreboot] [PATCH] Warn if we run out of MTRRs

Stefan Reinauer stepan at coresystems.de
Thu Feb 12 00:19:57 CET 2009

On 11.02.2009 18:11 Uhr, ron minnich wrote:
> I agree it's an emergency however :-)
> 10 minute boot times! call the hospital, the computer is sick!
> ron

I did a very similar patch two days ago. Sorry this is not against
Carl-Daniel's latest changes, but I thought I'd put it out for
discussion first.

There's one case when MTRR setup goes severely wrong, and that is all
those boards with UMA graphics onboard. That's all the 945GM boards, the
690 boards, some VIA boards, etc etc.

What the patch does is create a special case for UMA. It checks whether
there's an MTRR hole, and if there is none, it creates one for the UMA area.

With the patch applied my test board went down from 8 used MTRRs to 2
(one for RAM and one for UMA) and at the same time the complete RAM is

I remember there was a suggestion for a complete "optimal" MTRR setup
algorithm that attempts to always do the right thing with major
complexity. This patch is much simpler. It takes the most common case
and fixes it without trying to be perfect. So I think this is a good
solution for v2, and maybe someone wants to do the perfect thing for v3
at some point.

Comments? Acks?


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