MTRR vs. PAT and Intel Graphics

[Bruce Perens]

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

Here are the MTRRs when the fan control is set to "legacy":

reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
reg01: base=0x7f800000 (2040MB), size=   8MB: uncachable, count=1
reg02: base=0x7f700000 (2039MB), size=   1MB: write-through, count=1
reg03: base=0xe0000000 (3584MB), size= 256MB: write-combining, count=1

    Thanks

    Bruce