Digital Equipment Corporation PDP–7/A - S#118

Worcester Polytechnic Inst

The PDP–7 Service list (1972) shows that machine #118 (DEC #999999) was a PDP–7/A shipped to Worcester Polytechnic Inst around april 1967, and consisted of the following options –

OptionS#ShipDEC #Notes
138E000032 000000General purpose analog to digital converter, 6-11 bits selectable
139E000032 000000General purpose multiplexer control, 24 channel I/P for 138
149000081 0000004K core memory stack
177B000049 031023Extended arithmetic element
KA71A000018 000000I/O device package
KA77A000018 000000Processor unit
LT33CA3131650571014086Teletype Model 33 KSR

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

June 2024 – We were recently contacted by Aron Insinga about the fate of system #118, he emailed us saying -
"When I was a docent at The Computer Museum when it was still at DEC in Marlborough, MA.  Now of course, it's the CHM in CA.

Aron has given permission to use his information.  He goes on further -

"In the 1980s, The Computer Museum was still at DEC in Marlborough, MA (now, of course, it has become the Computer History Museum in CA) and I was a volunteer docent there while working for DEC and also taking grad. school classes part time at Worcester Polytechnic Inst. (Worcester, MA)."

"Normally classes met at a high school, but the first class of a semester was sometimes on-campus because the high school hadn't reopened yet after vacation.  So, one evening, when leaving a class on campus, I saw some old blue computer cabinets pushed out into the hall due to ongoing building renovations.  I peeked around them to see the front, and it was a PDP-7."

"I let people at the museum know about it, and DEC acquired it from WPI for TCM.  (I think they traded a new MINC system for it.)

"The PDP-7 must have had a DECtape drive at some point in its history because I was told a story about problem with a tape with a bad block, so someone toggled in a small program to make the drive seek to the block, and they looked under the tape where they found a squished fly on the bottom of the tape.  They used a fingernail to scrape the fly off of the Mylar (DECtape had Mylar on both sides of the oxide) and the block was repaired. "

There is no mention of any magnetic tape options (Options 5xx) in the service list, so they would probably have been later add-ons or retrofits.

If anyone knows, or hears more about the outcome of the Worcester Polytechnic Inst's PDP–7/A (S#118) please let us know, email us , or use our contact form.

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#118 - None at this time

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