The first supercomputer, IMO. It's an interesting machine, with a variety of innovations that later became standard: e.g. it has separate instruction and arithmetic units, with the former being in charge of all fetches, both instruction and data, as well as executing things like branch instructions; it also has a primitive form of pipelining ("Interlocks in the look-ahead unit ensure that nothing is altered permanently until all the preceeding instructions have been executed successfully.") Eric has a nice page about it: https://www.brouhaha.com/~eric/retrocomputing/ibm/stretch/ There's a good book about it: Werner Buchholz (editor), "Planning a Computer System: Project Stretch", McGraw-Hill, New York, 1962 Speaking of books, there's also a CDC 6600 book: Jim E. Thornton, "Design of A Computer: The Control Data 6600", Scott, Foresman, Glenview, 1970 Really gotta do that Bibliography! Noel