[...] Custom chips like these are a right pain to collectors/preservationists - when (not if) they fail, you essentially have to find another machine to raid for parts, and hope that one keeps going for a significant period (it may well fail a week later if you are unlucky). I decided to seriously collect only those machinews that were built with standard parts. That means I don't really bother with home computers after about 1980 (by that point, sales were high enough to make it worthwhile for the manufacturers to use gate arrays, etc). I generally prefer PDP11's, PDP8's, PERQs, etc which are built from standard parts. I do have a lot of machines that use custom chips, but I don't depend on them, and won't spend a lot of time hacking them, modifying them, etc. If I did, all that work could be useless when the chip fails. -- -tony ard12(a)eng.cam.ac.uk The gates in my computer are AND,OR and NOT, not Bill