Windows XP / Second GPU slows system down

[FrodoMiner]

Hi there,

I have a system with two 6970 running Windows XP (Catalyst 11..

When I mine with only one GPU, I get 420 Mh/s.

When I use the second GPU it slows to to about 250 for each GPU. So in total ~500. But it should be ~840.

I don't get this slowdown under Windows 7 (there I really get ~840).

Is there a known problem with Windows XP / OpenCL / two GPUs?

cheers,
F.

[soptik]

I had similar problem with two HD5830 GPUs on catalyst 11.8 - installed older version 11.6 and problem disappeared.

[GamingG]

Is your CPU bottlenecking?