ICW1_IC4
if ((val & ICW1_IC4) == 0) {
atpic_write(sc, icu, 0, ICW1_RESET | ICW1_IC4);
outb(pic->at_ioaddr, ICW1_RESET | ICW1_IC4);
outb(IO_ICU1, ICW1_RESET | ICW1_IC4);
outb(IO_ICU2, ICW1_RESET | ICW1_IC4);