AR_INTR_SYNC_ENABLE
REG_WRITE(ah, AR_INTR_SYNC_ENABLE(ah), 0);
REG_WRITE(ah, AR_INTR_SYNC_ENABLE(ah), sync_default);
REG_WRITE(ah, AR_INTR_SYNC_ENABLE(ah), 0);
(void) REG_READ(ah, AR_INTR_SYNC_ENABLE(ah));
REG_WRITE(ah, AR_INTR_SYNC_ENABLE(ah), sync_default);