PDP 11/03

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Nov 9 15:48:38 CST 2015

    > From: Jim Stephensn

    >> "extra wires to bring out clock & .. 110/300 speed change"

    > I am mainly asking if I want to hook up a terminal, can I get it going
    > with TD, RD and GND (or 2 3 7 on a DB25), or do I need to loop back any
    > of the other pins.

Well, without knowing how those extra pins work, it's very hard to say. Given
that _apparently_ one could change the baud rate externally (which means that
there's something in the cable - or at its other end - to do baud rate
selection), I'd _guess_ that a stock cable probably wouldn't work.

If you find a set of 11/780 prints, that _might_ include the specialized
cable for this beast, but short of that, you're talking signal trace/etc time.

    > I have several 4 port DLV boards, but want to go with this as a
    > reference. I paid a bit too much for it because it was "working"

Yes, but it doesn't have the cable!

Trust me, swapping to a DLV11-J is a fully known, simple, approach - not like
trying to work with a serial board with an unknown header pinout!

And that 'working' was some decades back! Who knows what the situation is now!

    > I don't want to screw it up by replacing cards.

If all you do is replace the M7940 with an M8043 in the same slot, that
shouldn't present a problem (make sure the M8043 is configured properly to be
the console, though; it is, however, very well documented).

    > I know even less about loading the backplane than I do about hooking up
    > a serial cable.

That's OK, I have recently run both M7940's and M8043's in my QBUS systems
here; they are a straight replacement (albeit using different cables - a
40-pin Berg/DuPont connector on the former, and 10-pin Berg/DuPont on
the second one).

    > I was hoping to get some idea whether the correct cable might be
    > available from someone on the list first, and buy it, or better, find
    > out how to spot them on ebay. I've had a lot of luck with the boards,
    > but none with finding listings for cabling.

Like I say, I expect the cable for the M7940-YA is a special item. As for
cables on eBay - fuhgeddabahtit!

Well, that's not quite true: seller 'conflandard' has some console cables for
sale, but I think only DLV11-J/11-23+ type (they are the same cable,
basically - the header pinout on the two cards is the same, the difference is
that the stock 11/23+ cable allows baud rate selection on the back panel -
but an 11/23+ _will_ work with a stock DLV11-J cable, provided the board is
jumpered correctly).

I've _never_ seen a DL11 type cable (with the 40-pin Berg/Du Pont connector)
for sale on eBay - well, not EIA ones. I think someone had an 20mA one for
sale, once.

    > and trying the 4 port cards. Most of them came from the cheap scrap
    > guy, so I don't know the state of them as well. I've seen some people
    > found there were duds in the pile.

_Most_ of the cards I bought from him worked (I haven't been able to try them
all, e.g. I don't have a working UNIBUS machine yet). The one exception was a
DLV11-J on which two of the four serial ports didn't work.

Once you have a working machine/board set, it all becomes much easier, of
course - you can swap boards around and see which ones are working. (If you'd
like, you can send me the DLV11-J, and I'll either send you a known
fully-good one, or test yours and send it back, along with the results. I've
done this for other people here.)

    >> I can supply both null-modem and non-null-modem cable diagrams (for
    >> DB25 connectors, already worked out; I have made DB9 serial cables,
    >> but not for direct connection to a DLV11, but could generate those
    >> too).

    > I'd love that

OK, let me go unearth the cable diagrams - or I suppose I could just look
at a cable, I have a couple of mostly-finished ones on the workbench at the
moment! :-)


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