Digital Equipment Corporation PDP–7 - S#41

Ministry of Public Buildings - National Gas Turbine Establishment Pyestock

The PDP–7 Service list (1972) shows that machine #41 was shipped to the UK Government - Ministry of Public Buildings in November 1965 and consisted of the following options –

OptionS#ShipDEC #Notes
50000129  Magnetic tape transport
57A000032  Automatic magnetic tape control, up to 8x 570's
75D000046  Perforated paper tape punch and control
149B00005011659999994K memory upgrade to 8K
175000019  Information collector expansion
1770000430667023755Extended arithmetic element
3540000140668032632Unknown option
444B000046  Perforated paper tape reader and control
520000017  Tape control interface for DEC type 50 transport
649000041  Teletype control.
KB03000007  Device selector expansion
KB03000009  Device selector expansion

For descriptions of the above options see the full PDP–7 options list.

The "Ministry of Public Buildings" shown in the 1972 18–bit service list the "Customer" as the Ministry of Public Buildings & Works, renamed in 1963 from the Ministry of Works, a department of the UK Government formed in 1943, during World War II, to organise the requisitioning of property for wartime use, this function was carried on after the war for Government building projects and the acquisition of equipment for the Ministry of Defence.

PDP–7 was installed in the computer facility (Building 574) of The National Gas Turbine Establishment Pyestock, which, for over fifty years was the UK's test and development centre for gas turbine engines.  In its time it was the largest facility of its type in Europe (if not the world), for the design, experimentation and testing of engines at Pyestock helped to usher in the jet age.  In amongst others it tested Concorde's Olympus jet engines in simulated supersonic conditions and the Pegasus engines for the Harrier Jump Jet, Pyestock's credentials were extremely impressive.  There are several web sites showing the once derelict and decaying site of one of the UK's premier research establishments, we would recommend  

During my time at NGTE Pyestock in the computing facility, in addition to the PDP–7 other computers in building 574 were - an SDS 9300 mainframe, a PDP11/45 (picture), and an ageing Elliott 803B which had been used for performance and design calculations on aircraft and engines and the processing of aerodynamic data.  All of this equipment was later replaced by an ICL 1904S running the George Mk8.64 operating system, two PDP11's and many remote PDP11/10's for data acquisition.  The PDP–7 was used for transient instrumentation whilst the SDS 9300 was used for steady state instrumentation, both machines can be seen at the bottom of this page, along with a photo of the SDS 9300 in operation and diagrams of the SDS 9300 (steady state) and PDP–7 (transient) installations.  Computer room layout.

A local backup shortened copy of the Pyestock computer room information and photographs is available for download, with thanks and acknowledgement to Simon Cornwell at

120 PDP–7 and PDP–7/A systems were forecast to be built in total, but the 1972 18–bit service list available (6.5Mb pdf download) only has details of the 99 known PDP–7 and PDP–7/A systems in the list at that time.  We do not have any information about the possible remaining 21 systems, who they were delivered to or even if they actually existed.

The PDP–7 appeared to have sold well into Government research and University sectors with 11 systems shipped to the UK alone, almost 10% of the forecast production run!  Serial numbers are concurrent for both PDP–7's and the PDP–7/A's, so the missing 21 could be of either type; however we are reasonably confident that the 99 systems shipped were the only ones that were ever built.

If you know of any information about any of the PDP–7 systems worldwide, options, location of existing systems, spare parts, ancillary bits, software, tapes or manuals, then please contact us.

Documents associated with PDP–7 S#41 - None at this time

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