Frontend for CDC 6600

Control Data never had a reasonable network front end architecture. Their 2550 controllers were ridiculously expensive and had very poor throughput. The UofM had developed a 6000 series I/O channel interface for the PDP-11, so I embarked on building a low cost high speed X.25 link interface leveraging new Western Digital silicon that automatically handled all the link layer HDLC handshake and media interface. The goal was to use it for both regular X.25 L3 packet service to support async terminals (TTYs and CRTs), but to also use it to eventually support Fuzzball IP routing such that we could use the Tektronix TCP/IP implementation on several CDC mainframes.

The hardware worked, but the UofM acquisition of a Cray-1 with it’s different front end architecture, and the shortsighted decision to invest in a huge new campus wide telephone system that principally supported circuit switched async terminal services, sort of eclipsed the project.