So I got myself a new Toshiba Qosmio x870 with a gtx 670 onboard. So far I'm very satisfied with it, but for some reason some overclocking options are unavailable to me. This is the first card I've tried overclocking. I've managed to get a stabe clock at 690 MHz and memory at 1550, but for some reason I can't touch the voltage. On Precision-X I get "This device is not supported", and on GPU Tweak, I can only take it lower but not higher than the standard 0.850. Help, please?