PDP-7 Digital Equipment Corporation PDP7 PDP-7

1964-65 saw the delivery of Digital Equipment Corporations 18 bit PDP7 series computer, a later revision, the PDP-7A was produced using R series modules, at the end of production 120 systems had been shipped. As a minicomputer the PDP7 had a cycle time of 1.75 microseconds and add time of 4 microseconds, I/O included a keyboard, printer, paper-tape and dual transport DECtape drives (type 555). Of the 120 PDP-7's that were sold quite a number being used in laboratory and data acquisition applications. D.E.C. provided an "advanced" Fortran II compiler, a Symbolic Assembler, Editor, DDT Debugging System, Maintenance routines and a library of arithmetic, utility and programming aids developed on the program-compatible PDP-4.

The PDP-7 was developed as a less expensive alternative to the earlier PDP range and it had an introductory price tag of only $72,000 for a minimal system configuration. Utilising core memory as did most machines of it's era, the PDP7's 18bit memory started at 4K words up-gradeable in 4k chunks to 64k. A range of I/O units was available including Calcomp plotters, DECtape magnetic tape, paper tape readers and punches, DEC 340 CRT display unit and the ubiquitous Teletype ASR33.

Of the 120 PDP-7's originally built only two are currently known to exist in some operable condition. One (S# 115) is apparently undergoing restoration in Oslo, Norway by Tore Sinding Bekkedal, but it is believed this machine had most of its guts modified to TTL 74 series logic at some point, which was then recovered when the machine was de-commissioned. The second at the University of Oregon (S# 113) was operated by Dr. Harlan Lefevre until his retirement when it was de-commissioned and recently donated to at a museum, it is believed this machine was fully operational after nearly 40 years with some 65,000 hours of use logged. There are unconfirmed reports of a third (S#47 ?) minimal configuration system at a museum in Australia. PDP-7

The PDP7's claim to fame was forged around 1969/70 when Ken Thompson used a scavenged PDP-7 at Bell Labs, the research arm of AT&T, to develop the operating system that later became Unix. This would have been one of the PDP7's #3, #34, #44 or PDP7A #149.

PDP is an abbreviation for Programmed Data Processor, coined by Digital and a Boston venture capital company American Research and Development. There was a perceived view at that time that with a limited world market for "Computers" of just a few hundred of what were seemingly big and expensive machines, requiring a dedicated computer center and a large supporting staff, the term "Computer" should be avoided as there was no money to be made in computers !, and so was born PDP - the "Programmed Data Processor".

Links -

Tore Bekkedal	Restoration of a PDP7 in Oslo. PDP-7
PDP7 data PDP-7	Possibly the largest archive of PDP-7 data available.
Unix history	Origins and History of Unix, 1969-1995.
History PDP-7	Unix - "The famous PDP7 comes to the rescue".
Wikipedia	PDP-7 entry at Wikipedia. PDP-7
PDP7 retires PDP-7	Goodbye to the PDP7 - "A Computing Pioneer Retires".
PDP7 Service list PDP-7	Details of 99 out of the 120 PDP-7 systems built.
Ken Olson	Biography and the story of DEC.

If you know of any more information about the PDP7, location of existing systems, spare parts, ancillary bits, software, tapes or manuals, then please let us know as a matter of urgency here. PDP-7

Our own library of PDP-7 information can be found here. PDP-7

PDP7 Service list (1972) PDP-7
The following list information was compiled from Digital Equipment Corporations 1972 18bit Customer Service List (kindly supplied by Bob Supnik), available here (6.5Mb pdf), and comprises the 99 known PDP7 and PDP7A systems on the list at that time. 120 systems were built in total, but at this time we do not have any information about the remaining 21 systems or who they were delivered to. The PDP7 appeared to have sold well into Government research and University sectors with 11 systems shipped to the UK alone, almost 10% of the production run !. Serial numbers are concurrent for both the PDP-7 and PDP-7A so the missing 21 could be either type.

Miscellaneous DEC information, manuals, data sheets, Etc. mostly for the PDP-7 of course !, but there is some PDP-11 and PDP-15 info in here as well.