PDP 11/03

jwsmobile jws at jwsss.com
Tue Nov 10 01:19:34 CST 2015

On 11/9/2015 7:31 PM, Noel Chiappa wrote:
>      > From: Jim Stephensn
>      > The 9400-YE has the cables that formerly went to the 11-780.  I'm not
>      > sure what it does. ... I'm not sure if the M9400 needs to be pulled or
>      > not to run the system.
> This one I actually can answer, since I've been looking for /780
> documentation: found some, but nothing on the hardware config of the console
> front end, alas. But I did discover about how the LSI-11 is interfaced to the
> VAX!
> The M9400-YE is a standard QBUS card for doing QBUS extension boxes; the QBUS
> leaves the M9400-YE (at the end of one box) on a couple of cables, which
> normally go to a M9401 (the sister card to the M9400) in the first slot of
> the next box.
> In the /780, the cables from the M9400-YE instead go to a card in the VAX
> CPU, an M8236 (the CIB - CPU Console Interface Board, I think). That board
> contains i) a bunch of ROM for the LSI-11, and ii) registers which allow the
> LSI-11 access to the inside of the /780 CPU - all of which are actually on
> the LSI-11's QBUS, logically/electrically.
> So, as to the M9400 - you can pull it, or leave it - there are no active
> components on it (although it does have termination pull-ups). Do pull the
> cables, though - they'd be un-terminated antennas...
>      > The M9400 seems to possibly be the Floppy boot and some other logic.
> There are some versions of the M9400 which contain ROM chips with a
> bootstrap. The M9400-YE, which you have, does not have these; it only has the
> headers for the cables, and the pull-up resistors.
>      > The line below that I clipped out, about the M7940-YA is for the
>      > adjacent card, and has no cable, just the open blue one waiting for an
>      > IDE cable to the back for serial connections.
Brain fart, I meant IDC ribbon cable.
> Err, it's not an IDE cable, although it is a 40-pin connector; it is used
> with special round cables, the wiring of which I described in an earlier
> message.
>      > A post by Tony Duell some years back states that the M7940-YA may have
>      > both a current loop and RS232 drivers for the port. That ... might
>      > explain the puzzling extra bit in the Dec module description about
>      > extra wires.
> No, the stock M7940 _already_ has support for both EIA and 20mA; see the
> DLV11 prints (MP-00055), pg. 6; the EIA stuff is in the top right-hand
> corner, the 20mA in the bottom right-hand.
> On that same page, lower left, note the baud rate clock generation; note
> that's entirely set by jumpers, so if there's some off-board way to set
> it in the M9740-YA, they must have modified this area of the board.
I'll pull and play in the next few days and post an update on that 
part.  Also will pull the antennas. :-)

thanks for the help.

I also have a buddy rummaging thru his pile for a sigma type box with a 
similar configuration which will help as well.  His may have what you 
suggested, the 4 port card and a cable I can copy (or abscond with).

One reason I asked here, you answered about finding the cables on ebay.  
Explains why I've not been able to stumble across any.  But the buddy 
mentioned above did a lot of dec maintenance and put these cables in a 
pile as he found them.. Problem again the cleaning and searching job 
right now has not turned up that bin box either.

However it will turn up.

I'm also watching Mike Ross play with an Altera Spartan board and he is 
going to try to get the 2030 emulation going,  It may motivate me to get 
off my thumbs and get out mine as well while my buddy searches for cables.

Also will order some parts to make the cable off the M7940.
Thanks again
> 	Noel

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