SPR_MMCR0_PMAE
mmcr0 |= SPR_MMCR0_PMAE;
mmcr0 &= ~SPR_MMCR0_PMAE;
mmcr0 &= ~(SPR_MMCR0_FC | SPR_MMCR0_PMAO | SPR_MMCR0_PMAE);