Re: MTRR problem in 2.4.7+ on Athlon+VIA? XFree86 can't write-combine

[Alan Cox]

> (WW) NV(0): Failed to set up write-combining range (0xd4000000,0x800000)
> to XFree86.0.log. XFree86 works, but things like MPEG playback seem a 
> bit slow.

Thats more likely because the Nv driver doesn't support Xv or Xvmc 
extensions, which most other drivers have and give you nice accelerated
overlay/colourspace/scaling for video playback.

> I assume this is because cat /proc/mtrr looks like this before X starts:
> 
> reg00: base=0x00000000 (   0MB), size= 128MB: write-back, count=1
> reg01: base=0xd0000000 (3328MB), size= 128MB: uncachable, count=1
> 
>  From reading the mtrr doco I gather that because 0xd0000000 + 128mb is 
> already set up as an uncachable range, "nv" can't set up 0xd4000000 + 
> 8mb as write-combining.

You can tweak the ranges yourself, deleting the uncachable one and putting
it back as two ranges

> I've searched all through the 2.4.7-10 source code and can't see 
> anything that I'm using that explicitly asks for MTRR_TYPE_UNCACHABLE, 
> so I'm a bit perplexed. I've had a good look around the web and 

The BIOS sets them up for you