FPGA VAX update, now DIY TTL computers

On 11/9/2005 at 11:49 AM Allison wrote: Automated wire-wrapping is less expensive than other methods, but doesn't give one the leve of control that other methods afford. It now seems incredible on what amounts to a 10 MHz mainframe, but wire length was a big part of the CDC 6600 design puzzle. I recall a friend telling me that his first assignment on his job at CDC was to take Cray's 6600 prototype and measure each coil of twisted pair to which had been attached a tag that said "tune" in preparation for actually manufacturing the thing. The old 6000-series taper-pin backplanes were a deep maze of wiring hanging here and there and the nanosecond-per-foot rule was an important part of the 6600 design. CDC continued to use taper-pin style backplanes long after other firms were using machine-wrapped backplanes, mostly, I suspect because of the ability to optimize propogation delays--and still retain the use of standardized "cordwood" logic modules. Cheers, Chuck