PDP-7

PDP-7
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 between them is not yet certain; one report is that the I/O system of the latter was re-designed to use the lower speed (and thus lower cost) 'R' series FLIP CHIPs. 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 recently been thrown away.

Emulation

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

External links

• PDP-7 - Original PDP-7 documents
• Digital Equipment Corporation PDP-7 - Extensive site with a large amount of material
  • PDP-7 brochure
• "The famous PDP-7 comes to the rescue" (Bell Labs' Unix history)
• DIGITAL Computing Timeline - 1964 - PDP-7 entry
• PDP-7 Definition
• PDP-7A minicomputer - from Paul Allen's collection at the LCM, includes several images