IRQ_CASCADE
REGVAL8(HTB_IO_BASE + IO_ICU1 + PIC_ICW3) = ICW3_CASCADE(IRQ_CASCADE);
REGVAL8(HTB_IO_BASE + IO_ICU2 + PIC_ICW3) = ICW3_SIC(IRQ_CASCADE);
irq = IRQ_CASCADE;
imr1 &= ~(1u << IRQ_CASCADE);