I remember how patient the designer was when he sat me down to explain to me that you don't need an interrupt from the 8563 indicating that an operation is complete because you can check the status ANY TIME mearly by stopping what you're doing (over and over) and looking at the appropriate register, (even if this means banking in I/O) or better yet sit in a loop watching watching the register that indicates when an operation is done (what else could be going on in the system besides talking to the 8563 ???) Our running gag became not needing a ringer on the phone because you can pick it up ANY TIME and check to see if someone's on it, or better yet, sit at your desk all day picking the phone up. Even in the hottest discussions someone would suddenly stop, excuse himself, and pick up the nearest phone just to see if there was someone on it.