AMD 760 PCI Problem

AMD 760 PCI Problem

[Jason Howard]

Hello All,

I am having trouble getting decent PCI throughput on either of my AMD
system (both using the AMD 760 chipset.)  I am moving a high definition
frame into a pci frame buffer.  This process takes somewhere around 100
ms on my Dual Xeon system, however on the two AMD systems I have tried
it is taking about 1 sec (1000 ms).

The two systems I have tried are a single processor athlon system and a
dual processor athlon system.  (Both use the AMD chipset .. the single
uses the AMD760 and the dual uses the AMD760MP).  Both boxes are running
kernel 2.4.6.

Any suggestions?

Thanks,
Jason

Re: AMD 760 PCI Problem

[Gérard Roudier]

On Tue, 4 Sep 2001, Jason Howard wrote:

> Hello All,
>
> I am having trouble getting decent PCI throughput on either of my AMD
> system (both using the AMD 760 chipset.)  I am moving a high definition
> frame into a pci frame buffer.  This process takes somewhere around 100
> ms on my Dual Xeon system, however on the two AMD systems I have tried
> it is taking about 1 sec (1000 ms).
>
> The two systems I have tried are a single processor athlon system and a
> dual processor athlon system.  (Both use the AMD chipset .. the single
> uses the AMD760 and the dual uses the AMD760MP).  Both boxes are running
> kernel 2.4.6.
>
> Any suggestions?

Check the settings of the MTRR's against the frame buffer window.

If they appear not to be configured correctly, you just have to ask the
kernel to fix the thing (a MTRR defined for Write Combining must contain
the address range of the frame buffer).

see: linux/Documentation/mtrr.txt by Richard Gooch for details.

  Gérard.