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A PDP-7 in Oslo, Norway
Manufacturer: Digital Equipment Corporation
Year Introduced: 1965
Form Factor: minicomputer
Word Size: 18 bits
Logic Type: PNP Transistor FLIP CHIPs
Memory Speed: 1.75 μsec
Physical Address Size: 15 bits (32K words)
Virtual Address Size: 13 bits (direct), 15 bits (extended)
Operating System: DECSYS-7
Predecessor(s): PDP-4
Successor(s): PDP-9
Price: US$72K

The PDP-7 is a minicomputer produced by DEC, introduced in 1965; with a low cost, it was cheap but powerful. There were two models, the second being the -7/A, but the difference is not yet clarified. Approximately 120 are thought to have been built.

The PDP-7 was the third of Digital's 18-bit machines, with essentially the same instruction set and architecture as the predecessor PDP-4 and successor PDP-9. It was the first wire-wrapped PDP. It was the first to use their Flip-Chip® technology, but also included the older System Modules.

In 1969, Ken Thompson wrote the first UNIX system in assembly language on a PDP-7, then named Unics as a somewhat treacherous pun on Multics, as the operating system for Space Travel, a game which required graphics to depict the motion of the planets. A PDP-7 was also the development system used during the development of MUMPS at MGH in Boston a few years earlier.

There are a few remaining PDP-7's still in operable condition. One under restoration in Oslo, Norway, has been thrown away.


The PDP-7 can be emulated with SIMH. DECSys, Unix, Space Travel and some other software is available and can run on the emulator.

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