[LinuxBIOS] Opteron caching of device memory

Myles Watson myles at pel.cs.byu.edu
Thu Jun 14 22:33:14 CEST 2007

> On 06/13/2007 09:39 AM, Myles Watson wrote:
> > I'm using LinuxBIOS on my Tyan s2892.  I have a device that maps a lot
> > of the memory space, but I'm struggling trying to get the Opteron to
> > read and write to my device in larger blocks.  I have set the variable
> > MTRRs in the device driver to writeback (witnessed by /proc/mtrr), but I
> > still get 64-bit accesses instead of 64-byte (cache line).
> Some time ago I officially asked an AMD's rep about this. Someone from AMD
> unofficially said that MemIO can be only Write-Combined. And I gave up
> with caching.

I'm having the same trouble. Even though the MTRRs are set for write-back,
it acts as if it were write-through. I'll keep looking, because it's
important to my project.

Thanks for your help and suggestions,

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