MTRR vs. PAT and Intel Graphics

[Jesse Barnes]

On Friday, June 1, 2007 11:57 am Jesse Barnes wrote:
> On Friday, June 1, 2007 11:06 am Bruce Perens wrote:
> > Jesse Barnes wrote:
> > > That said, it seems odd that a simple fan configuration setting
> > > would eat up four whole MTRRs.  What does /proc/mtrr look like
> > > with and without the fan setting enabled?  Linux could do a
> > > better job of verifying and reprogramming MTRRs in many cases
> > > than it does currently.
> >
> > Here are the MTRRs when Intel QST fan control is enabled on the
> > motherboard
> >
> > reg00: base=0x00000000 (   0MB), size=1024MB: write-back, count=1
> > reg01: base=0x40000000 (1024MB), size= 512MB: write-back, count=1
> > reg02: base=0x60000000 (1536MB), size= 256MB: write-back, count=1
> > reg03: base=0x70000000 (1792MB), size= 128MB: write-back, count=1
> > reg04: base=0x78000000 (1920MB), size=  64MB: write-back, count=1
> > reg05: base=0x7c000000 (1984MB), size=  32MB: write-back, count=1
> > reg06: base=0x7e000000 (2016MB), size=  16MB: write-back, count=1
> > reg07: base=0x7e800000 (2024MB), size=   8MB: uncachable, count=1
>
> Wow, that looks like some sort of best fit algorithm gone horribly
> wrong. :)  It doesn't even create a new uncachable window for the QST
> fan control (which is presumably ACPI or SMM based).  Have you
> reported this to your BIOS vendor?

Oh, and my guess is that this would affect pre-XP versions of Windows 
too, which may help motivate your system vendor. :)

Jesse