Just to remind you that you need to vacate some threads to feed the GPU. And as far as my experience goes, Seti's AstroPulse tasks need more voltage (a.k.a more stable machine) than MultiBeam ones to avoid invalid results.
I need @Kiska to validate my statement, though.
Hrm I was mentioned?
Oh, yes the SETI Multibeam OpenCL app requires a full CPU core to support the GPU, the OpenCL AstroPulse app not so much but still requires a bit of CPU support. So that should answer your question
