Slow down of GPUs (85% usage)

[zimpixa]

Hi there,

For today my problem is:

When running two GPUs they cant be set with argument -f0, because GPU usage drops to around 80/93%. Im wondering, if there is something wrong with my rig or its common problem.

Spec:
XP sp3
C2D E7400 @2.8GHz
Gigabyte P31-ES3G
CC 11.4
SDK 2.1 (same problem with 2.4)
poclbm (poclbm with phatk,phoenix got this problem even bigger)
GPU1: 5850 Xtreme
 -f30 -r5
currently avg 380MHash while both cards running, solo 387MHash (on same '-f')
GPU2: 5870 Vapor
 -f2 -r5
currently avg 419MHash while both cards running, solo 435MHash (on same '-f')

[padrino]

I was having similar problems, the phatk kernel was the issue as long as I don't use it my mining rates end up higher.