Hi, it's really easy: Unlike an IBM, each Slot has a fixed set of I/O addresses. So the address depends on the slot the thing is in. Get the hardware manual (from The Byteworks), it will tell you everything you need to know. Oh, and don't bother with the schematics in that book, use a GAL to decode addresses. Much nicer, more flexible, less costly, etc. Have fun Soenke