<Yes, but it's possible to make replacement parts for an auto engine. If <there's simply no more of a certain processor available, what do you do <besides make a replacement out of custom chips? Thats bogus as finding 8080s is not hard and in a pinch a 8085 or z80 (both more common) could be used as it's nearly as old. In practical terms a front pannel machine based on a z80 would prove a useful learning tool and prove to those that think it's cool why they are gone. ;) It doesn't have to be an altair or IMSAI clone. Th real clone question is, does one copy all of the faults and bugs or does one clean it up so that it's reliable in function? Allison