In a previous post, someone mentioned he couldn't remember the various comm port addresses and IRQs. So, without further fanfare, Comm1=03F8H Comm2=02F8H Comm3=03E8H Comm4=02E8H Common IRQ assignments are IRQ3 for 2 and 4, and IRQ4 for 1 and 3. And obviously, you can't have 4 comm ports and only 2 IRQs. The way I remember the IRQs is that for even comm ports, the IRQ is odd, and vice versa. 73 Ed