From: Tony Duell <ard(a)p850ug1.demon.co.uk> as Yes, 10, 18, 24 bits are some of the more interesting of the oldies. I've found with builing or at least designing on paper that unless you want to do an existing machine there is little reason to do what others have. Sizes like 8 and 24 bits are very useful but 4bits can make the ALU core very simple without ruling out complex capability (though slow). The other direction is control oriented machines that are programable but otherwise specific. Allison