Help identifying UNIBUS PDP-11 CPU upgrade

Noel Chiappa jnc at
Sat Jul 1 13:02:54 CDT 2017

    > From: Josh Dersch

    > There's a 20-pin header on the CPU upgrade board which connects to the
    > front panel. ... the programmer's panel loses most of its functionality
    > .. but the HALT/SS and BOOT switches are functional with the cable
    > connected. ... With the 20-pin cable from the front panel disconnected,
    > the HALT and BOOT switches are non-functional.

That's interesting. There aren't 'HALT' and 'BOOT' lines in that 20-conductor
cable; the data sent across that cable is keyboard scan codes, which the 8008
on the KY11-B quad board has code to decode. So the upgrade board must have
something to scan the KY11-B keyboard, and translate the scan codes...

    > If so, the one on the CPU doesn't appear to conflict with the M7856 I
    > already have in the /34.

Hmm, maybe one of the undocumented jumpers/switches (forget which this card
has) is an enable/disable for an on-board serial console?

The other possibility which just came to mind (thinking about the fact, above,
that apparently the upgrade board is prepared to replace the M7859 of the
KY11-B, instead of leaving it in situ, and interacting with it over the
backplane, the way the -11/04-34 do) is that that connector is for use with
the KY11-LA - instead of plugging the cable that comes out of the KY11-LA into
the backplane, it plugs into the replacement card instead?

It would be very interesting to know what chips that 10-pin header is
connected to!


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