Also I fired up a CPU miner on that same core, Doesnt slow down the gfx cards at all and atleast the 99% useage is getting sent somewhere productive.
i just tried it for fun, but it reduces my gpu speeds to cpu speeds (under .5Mhs) so i would have to use a core not being affinity by the gpus. not worth it, would be more effectiev for me to oc my gpus a bit more.