 Seymour Cray soon became the chief designer, though at the time of CDC's formation he was still in the process of completing a prototype for the Naval Tactical Data System (NTDS), and he did not leave Sperry to join CDC until it was complete.The M-460 was Seymour's first transistor computer, though the power supply rectifiers were still tubes.CDC started business by selling subsystems, mostly drum memory systems, to other companies.