Since the programmer's model of the machine is 32-bit, and the addressing and bus width have negligible performance or capacity impact in any "retro" era system, it is clearly a 32-bit system from a software perspective--which I presume is the only relevant measure in the Retrochallenge. If I were drawing the line in 2006, I would draw it at no larger than 24-bit registers. That would eliminate essentially all "modern" architectures (which is the point, right?). -michael The Atari TT-030 in 1991 and Atari Falcon in 1992 did 24 bit registers. Be a shame to knock those out. No matter that restrictions you add, my Atari 800 (from 1979) still qualifies. :D Greg