The GE-645 was designed in 1965 by John Couleur and Edward
Glaser at MIT. It had several security levels and
instructions for handling virtual memory. Addressing used
an 18-bit segment in addition to the 18-bit address,
dramatically increasing the theoretical memory size and making
virtual memory easier to support.
Design of the GE-645's successor, the GE-655, started in 1967.