Digital Equipment Corporation PDP–7/A - S#126

Cambridge University

The PDP–7 Service list (1972) shows that machine #126 (DEC #010069) was a PDP–7/A shipped to Cambridge University in February 1966 and consisted of the following options –

OptionS#ShipDEC #Notes
149000092  4K memory upgrade to 8K
177B000008  Extended arithmetic element
5500000281070080896DECtape control, (up to 4x 555's)
KA71A000025  I/O device package
KA77A000025  Processor unit
TU55000051  Single DECtape transport

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

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/A S#126 are –

A find in DECuscope Volume 10 1971, the newsletter of the Digital Equipment Users Society, has unearthed an article by A. R. Atherton of the Cavendish Laboratory, Cambridge, England (PDP–7/A S#126), entitled "MODERNIZING A PDP–7", where a new 16K core store was fitted to their PDP–7 and the opportunity taken to reduce the cycle time of the computer from 1750 nsec to 875 nsec, doubling its speed.

Documents from the Cambridge University Computer Preservation Society detail the TITAN computer system which in the history of Cambridge University was the system between EDSAC 2 and Phoenix.  This system included a data link to PDP–7/A S#126.

From the University of Cambridge (UK), here is a brief informal history of the Computer Laboratory.

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