in November 1961. The hardware was replaced with a modified IBM 7090 in 1962 and later a modified IBM 7094 called the "blue machine" to distinguish it from the Project MAC CTSS IBM 7094. Routine service to MIT Comp Center users began in the summer of 1963 and was operated there until 1968.

A second deployment of CTSS on a separate IBM 7094 that was received in October 1963 (the "red machine") was used early on in Project MAC