Miners, did the new Catalyst version 11.9 fix 100% CPU usage issue for you? what's the best version of Catalyst to use for mining?
Catalyst 11.9 resolved the issue for those mining on single GPUs but not multiple GPUs (including single cards which contain multiple GPUs like the 6990 and 5970). You can try setting the
-f flag to higher numbers until CPU usage is reduced or try setting
-aggression to 10 or lower. Note that these settings might reduce your hashrate significantly depending on how aggressively you change them from defaults.
The bug in question was introduced in Catalyst version 11.5 and at the time affected only multi-GPU setups. It remained in place for version 11.6 and in 11.7 actually began affecting single-GPU systems as well. In 11.9 the single-GPU bug was fixed, but the multi-GPU bug is still in place. There is a beta release of 11.10 available but I've not heard anything about whether it fixes the 100% bug or not.
A quick search shows that the 11.4 drivers are still available for 32 and 64 bit systems. Assuming you don't need anything that the newer drivers offer for non-mining purposes, 11.4 is probably your best bet. If you're running dedicated rigs it's definitely your best bet.
Edit: It appears that 11.10 did not fix the multi-GPU bug so 11.4 is still your best bet.
I still get 100% cpu when with Catalyst 11.9 when I use the -f1 flag on poclbm. I fixed it by bumping up to -f4, which gives me a slightly higher hash rate than the -f6 I had to use previously to fix cpu usage.