PDP 11/23 help needed

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Wed Apr 22 09:49:52 1998

On Apr 22, 0:16, Seth J. Morabito wrote:
> 1) The M8047-CA boards need to be wire-wrapped to assign their
> address vectors -- they're combination MOS RAM and Async EIA,
> and I have no docs for them. Can anyone guide me to some info,
> or tell me how to jumper one of them to be console serial
> port, and the other to be next in line on the bus?
> The wire-wrap pins have absolutely no markings on them, not
> even any single-letter or number labels, so this one could
> require ASCII-art to describe :)

There are umpteen pages of link settings in the manual. I'm not keen to type
all that in ATM, but if no-one else answers in a few days, I might scan the
pages and accidentally store them on my website (copyright? wassat?)

> 2) Same as above, but for the M8044-DB boards. I could put one
> of these in with the M8047's to get a full 64Kword of RAM, yes?
> Does anyone know what the DIP-switch settings for these boards
> are?

Yes, but I'm not sure why you say "full" and 64Kword" together :-)
32KW (64KB) is the limit for 16-bit addressing, or 128KW (256KB) for 18-bit
addressing. Ignoring the I/O page, that is.

The MSV11-D addresses memeory on any 4KW boundary, set by the switches.
SW1-5 = A13, SW1-1 = A17. Right under Sw1-5 are 2 wrapped links (6 posts) that
set the memory *size* which you shouldn't need to change. There are 3 posts
labelled 6,5,7 which set parity/no-parity; they should be jumpered 5-7 to set
no parity for the -Dx. There are 3 posts labeled 2,1,3 near the B
edge-connector which enable/disable use of the bottom 2K of Bank7; 1-3 to
disable that. Lastly, there are two sets of power jumpers just above the notch
between the connectors; these are used to set battery/no-battery option.

> 3) I'd love to have the RK05 controller in there, in the hopes
> that someday I'll have an RK05 to play with. Just like the
> above... How do I jumper it, and where (physically) in the
> Bus should I put it?

Usually after the other IO/memory options.

> 4) Actually, that raises a good question. All of these boards
> are single-height (1/2 the width of the Q-bus backplane).
> I know there is some special physical layout the boards should
> use when they populate the backplane, but what is it?
> My best (probably wrong) guess right now is:
> CPU in row 1, slot 1 (is that left or right?),
> M8047's in row 2, slots 1 and 2,
> M8044 in row 3, slot 1,
> M7269 in row 4, slot 1, DSD controller in row 4, slot 2.
> Does that make any sense? Should the CPU only live in the
> first row, not RAM? I seem to remember something like this
> from the darkest depths of my mind, but I don't remember
> for sure.

The processor should go in slot 1 (top) because that's the only one with
connections to the RUN signal (used for the front panel light), though it will
work elsewhere apart from that. Except in BA23/BA123 cabinets with H
backplanes (see below).

Normally you'd put the memory next, then the I/O, starting with the options
that need the best CPU response (which is often the SLUs, not the disks).

As to which side, that depends on the type of backplane. There are two main
types; "serpentine" (aka "zigzag") which have Qbus in both A-B and C-D slots
(A-B are the left side as you look into the card cage from outside, with slot 1
at the top), and "straight", which have QBus in the A-B slots, and C-D
interconnect in, surprise surprise, C-D. In serpentine backplanes, the slots
are wired in the order 1A/B, 1C/D, 2C/D, 2A/B, 3A/B, 3C/D....

There are variations in microPDP-11 backplanes, where the first 3 (BA23
cabinet, H9278-A backplane) or 4 (BA123 cabinet) slots are wired straight (Qbus
in A-B, interconnect in C-D) and the rest are serpentine. That's to allow PMI
memory in the top, and lots of dual-width options below.

H9273, H9276 are straight. H9270 and H9275 are serpentine. You probably have
an H9273, if it's an early 11/23. Later ones had H9276's (22-bit instead of
18-bit). There should be a label somewhere on it. That means you probably
want all the cards in the left side, and none on the right.

There are also odd ones like the various H9281-x which are only dual-wide, and
the DDV-11 backplane which is hex wide, with Qbus in A/B and C/D, and
interconnect in E/F.

> 5) OK, simple question, one I've wondered about but never bothered
> getting answered because I felt like a complete idiot moron
> asking it: Does the QBUS need to be terminated by a special
> card in any way, in order to work?

Usually, yes. H9275 and H9278 backplanes have built-in terminator options.
 Others need a terminator card, such as a BDV11. The normal termination is a
nominal 120 ohms, usually as 180/390-ohm resistor packs.

> 6) What's the pin-out on the M8047 EIA ports? They're 9-pin Berg
> connectors, and I need to build a cable for them to connect
> either to 9-pin or 25-pin PC-style serial in order to set up
> any kind of console terminal.

Looking at the back of the card, components uppermost:

      | |
      | 9 7 5 3 1 |
      | |
      | 10 8 6 4 2 |

 1 UART clock in/out (depending on a link, not all SLUs have this)
 2 signal ground
 3 transmit +
 4 transmit -
 5 signal ground
 6 index - no pin
 7 receive -
 8 receive +
 9 signal ground
10 some SLUs have +12V here, from a current-limiting resistor or a fuse, to
    supply a converter. I use it with a 1K series resistor to provide a
    pseudo-DTR signal for some terminals.

For normal RS232, link 7-9, and use 3 as XMIT, 8 as RCV, 5 as SG, and ignore
pin 4.

> 7) Anyone know what the Data Systems Design board is? It has
> "RX" stensiled onto the board near the jumper block, among
> other things like "BOOT", so I assume it's some sort of RX01
> or RX50 controller or some such.

Much more likely to be RX01 or RX02 than RX50. What kind of connector does it
have? If 34-pin, it might be RX50 but could be like the Baydel units that use
a 34-pin connector but are actually an SA800 interface. If 50-pin, probably an
SA800/801 interface for 8" drives.

> WHEW, that's _too_ many questions. Anyone who can tackle one of them
> gets my respect, and you may award yourself one cookie.

I prefer flapjacks :-)

> I'd like to piece this system together and get it working to the
> point where I can play with it and at least fiddle with the monitor
> again, playing with Octal. And I'd dearly love to put it in a
> proper DEC desk-side rack with an RK05, but that comes later...

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York
Received on Wed Apr 22 1998 - 09:49:52 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:30:41 BST