INT_CTL1
outb(INT_CTL1, 0); /* ICW2 for master */
outb(INT_CTL1, (1 << CASCADE_IRQ)); /* ICW3 tells slaves */
outb(INT_CTL1, ICW4_AT); /* ICW4 */
outb(INT_CTL1, (INT_MASK = ~(1 << CASCADE_IRQ)));
outb(irc_no ? INT2_CTL1 : INT_CTL1, ~(1 << (irq_no >> (irc_no * 3))));
outb(INT_CTL1, INT_MASK);