Page "Digital Equipment Corporation" Paragraph 20

When DEC introduced the PDP-1, they also mentioned larger machines at 24, 30 and 36-bits, based on the same design.

During construction of the prototype PDP-1, some design work was carried out on a 24-bit PDP-2, and the 36-bit PDP-3.

Although the PDP-2 never proceeded beyond the initial design, the PDP-3 found some interest and was designed in full.

Only one PDP-3 appears to have been built, in 1960, by the CIA's Scientific Engineering Institute ( SEI ) in Waltham, Massachusetts.

According to the limited information available, they used it to process radar cross section data for the Lockheed A-12 reconnaissance aircraft.

Gordon Bell remembered that it was being used in Oregon some time later, but could not recall who was using it.