The Nokia telephone exchange architecture DX 200 had and still has this: everything is replicated. This allows things like switching boards while the exchange is running, with nothing bad happening. Runs its own microkernel DMX, but can host full ones, too – Nokia DX 200 - Wikipedia
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Less broken link
Thanks for spotting the dead link Ben - I’ve updated the head post accordingly.
It seems that both happened: the USAF’s Cambridge Research Lab at Hanscom Field was persuaded to buy two PDP-1s, while the Scientific Engineering Institute built a “real” PDP-3 itself using DEC’s plans, effectively a (rather expensive) kit build. See p. 82 of the (very interesting) 1992 Digital at Work book (ISBN 1-55558-092-0) and pp. 32-35 of the CHM oral history of Gordon Bell, part 1 (June 2005). On the other hand, in Digital at Work (p. 82 again) Bell was emphatic that there was never even a design for a PDP-2:
“The PDP-2 was a mythical machine number, reserved in case we wanted a 24-bit computer,” says Gordon Bell. “It was never defined on paper. The PDP-3, a 36-bit computer, was defined and one of our customers actually built one using Digital modules. We almost got an order for a PDP-3 from the Air Force, but Harlan Anderson and I persuaded them to take two PDP-1s—two 18-bit machines instead of one 36-bit machine.
Apparently Cray was a little overconfident: it turned out it wasn’t just farmers, physicists were quite worried about error-checking too:
My boss at [the US National Center for Atmospheric Research] — the wonderful Glenn Lewis, who had gotten his PhD from von Neumann — was mild mannered, super smart, and terrific to work for and with. The only time I saw him lose it — and it was a total meltdown — was when he found out — after the delivery of our 6600 — that it had no parity bits or checking in the main memory. When confronted, Cray said he wanted to use every core in memory for “information bits”!
Apparently the 6600 cost about $2.4 million US, about ten times as much in today’s money, so that does seem like a bad thing to find out so late in the day.
I have seen Fortran code which had CDC 6600 #ifdefs. (Yes, Fortran code and ifdefs, you read that right.)
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