# [SOLVED] Problems with write-caching / mtrr & intel 810

## shepmaster

Hey all, I just had to jump through some xorg hoops to get my i810 driver working again. My resolution is back to normal, but it *feels* slow. I saw the following in my Xorg.log.0

```

(WW) intel(0): Failed to set up write-combining range (0xc0000000,0x10000000)

```

So I poked at my mtrr, which seems... wrong:

```

# cat /proc/mtrr 

reg00: base=0x00000000 (   0MB), size=65536MB: write-back, count=1

reg01: base=0x7f800000 (2040MB), size=   8MB: uncachable, count=1

reg02: base=0x7f700000 (2039MB), size=   1MB: uncachable, count=1

reg03: base=0x80000000 (2048MB), size=2048MB: uncachable, count=1

```

Am I wrong in thinking that 65536MB is a bit... large? I do have 2 GB of RAM, so 2048MB doesn't seem too wrong.

I also can't add a new mtrr record:

```

# echo "base=0xC0000000 size=0x10000000 type=write-combining" > /proc/mtrr 

bash: echo: write error: Invalid argument

```

Thanks for any tips or tricks!Last edited by shepmaster on Wed Mar 05, 2008 2:59 pm; edited 1 time in total

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## shepmaster

Well, I decided to poke around and did the following:

Remove and recreate the main memory region

```
# echo 'disable=0' >| /proc/mtrr

# echo 'base=0x00000000 size=0x80000000 type=write-back' >| /proc/mtrr
```

Remove the dubious 2GB partition

```
# echo 'disable=3' >| /proc/mtrr
```

Then I added my video card range

```
# echo 'base=0xC0000000 size=0x10000000 type=write-combining' >| /proc/mtrr
```

Now things seem to be working again.

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