I recently switched from WinXP32bit to Windows7. While under XP poclbm took about 5% CPU Time of one core, now it uses one core with 100%. Is there a specific reason for that?
I now use AMD/ATI OpenCL1.1 and poclbm with poclbm.exe -device=0 -v -w128 -f 60. MHash/s is about the same I had with XP.
This is a common problem whose cause is not well known. You can try switching miners, switching flags, or switching OpenCL versions. Usually you can find a combination that resolves the problem. I've seen this question asked several times and I've not yet seen a solid answer.
I believe the blame lies on AMD's driver. I've heard that 11.9 might have fixed the bug, but am not sure. 11.6 works for me on Debian Squeeze without the cpu usage bug.
AMD Catalyst drivers have a bug which result in 100% CPU usage.
The current drivers (11.9 as of writing) solve this bug for SINGLE GPU systems but MULTIPLE GPU systems are still affected by the "100% CPU bug". This isn't anything that can be fixed in software it must be fixed by AMD driver team.
The 11.10 preview driver also doesn't (at time of writing) solve this 100% bug on multiple GPU systems.
I have heard (but can't personally confirm) that Nvidia drivers also have a similar bug with OpenCL drivers.
