NV_PRAMDAC_DACCLK_SEL_DACCLK
head << 8 | NV_PRAMDAC_DACCLK_SEL_DACCLK);
NVWriteRAMDAC(dev, 0, dacclk_off, dacclk | NV_PRAMDAC_DACCLK_SEL_DACCLK);
dacclk & ~NV_PRAMDAC_DACCLK_SEL_DACCLK);