The multi-CPU PDP-11/74 MP

Hardware
1

I didn’t know about this… and I found some photos. See here and here.

image
image901×424 104 KB

(image from Sergey Oboguev’s livejournal, from Dave Carroll’s G+ album post “PHEANX (PDP-11/74mP)”)

The PDP-11 FAQ says:

Probably the most famous PDP-11 that never was. Designed as a 4-way multiprocessor with four 11/70 processors clustered around shared memory. Configuration was SMP. Furthermore, the processors, which had been originally designed as FORTRAN crunchers, were to be equipped with the Commercial Instruction Set (CIS) for Cobol applications. Prototypes were built and a number of alpha units installed, but the product never came to market. Reasons for it never being shipped are various and may be apocryphal: the backplane would have been so complex to be almost unmanufacturable; the cost due to the complex backplane would have been too high; the 11/74 with CIS would have blown the new VAX-11/780 out of the water in commercial applications. Those that truly know are not talking :slight_smile:

3 Likes
2

I need a cold shower… be right back…

1 Like
3

There’s an interesting and informative discussion going on about the 11/74, including some insiders from back in the day, on the PiDP-11 list.

DEC kept running them internally, and as far as I know, the last one was shut down in 2001 or so.

I have a simulated one running. That is Mim.Update.UU.SE. Just telnet to it, and log in.

CASTOR and POLLUX were the same system. CASTOR was for when the system was running as a quad. Sometimes they would split the system into 2 duals and the second system would be POLLUX.

4

See also the Gunkies Wiki page on PDP-11/74:
https://gunkies.org/wiki/PDP-11/74