Personally I think the Benchmark thing to choose a CPU Core is a lot of wasted time, also shutting down 1-2 or 3 Cores. I tested shutting down Cores (3 on my HT 12 Thread E980x's) and didn't see 1 bit of time difference or Credit difference for either my 6990 or 590's ... I also did a little looking around at guy'z Box's that say their using this Core or that Core & my Wu's run just as fast as theirs just using AUTO Select unless they have theirs Overclocked more than mine.

I also discovered a long time ago that setting the # of CPU's to use to <ncpus>0</ncpus> that the GPU's WU from any GPU Project will automatically use the amount of CPU that it needs to use without any input from me. I don't know how that works since I set it to use 0 CPU but it must be something the BOINC Client Automatically adjusts for when running GPU Wu's because at times depending on the GPU Wu's I'm running I have 2-3 or 4 CPU's running on a Quad Core or 4-5 or 6 running on a 6 Core Box.

I know that works for Client 6.12.34 & up but not sure about anything lower than that ...