NV_PCRTC_850
regp->crtc_850 = NVReadCRTC(dev, 0, NV_PCRTC_850);
regp->crtc_850 = NVReadCRTC(dev, head, NV_PCRTC_850);
NVWriteCRTC(dev, head, NV_PCRTC_850, regp->crtc_850);