What motherboard are you using? What is the card configuration in the PCIE slots? What kind of drives are you using? Is the BM card using a “shared” PCIE slot with the GPU? If you’re using multiple x16 slots it could be your GPU has been bumped down to x8.
After being referred here by Zoltán, I will echo what Ladin and chq has said. Single threading holds back Resolume more and more as CPU development progresses, favoring cores over clock speeds. This optimization problem is only going to get worse.