PDP-11 bootup

John Floren slawmaster at gmail.com
Thu Mar 26 08:48:15 CDT 2009

On Thu, Mar 26, 2009 at 4:32 AM, Pete Turnbull <pete at dunnington.plus.com> wrote:
> On 26/03/2009 05:34, John Floren wrote:
>> Here is a complete list of the boards in my system, as removed from
>> top to bottom (this was a rack mount unit)
>> 1x M8192
>> 1x M7195
>> 1x mysterious quad-height board from DEC; I can only find labels
>> saying "PC304135-I4", "0202", and "Rear PSW1-0"
>> 2x Matrox QRGB-G-64/4 boards
>> 1x Matrox QVAF-512/8A (or QVAF-5/2/8A, hard to read)
>> 1x Dataram 40903 (memory? It's got tons of little ICs)
>> 1x M7941
>> 1x M7555
> M8192 is a dual-height KDJ-11A for an 11/73 and as Jerome pointed out that
> has no bootstrap.  Possible reasons for being left at the ODT prompt include
> the HALT switch being on, or there being no bootstrap anywhere else.
>  However, the next board, M7195, is a multifunction MXV-11B, which probably
> does have a bootstrap on it.  Look for a pair of EPROMs on it.  The manual
> is around the net, and I expect there's a copy on bitsavers.

The M7195 appears to have two EPROMS, labeled 145E4 and 146E4, which
Google seems to say is the correct rom set for a /73

> The KDJ-11 doesn't have all the ODT commands that some earlier QBus
> processors have.  "G" is the command to "Go" to an address.  "P" is the
> command to "Proceed" without initialising the bus.  The only other commands
> on a KDJ-11 are slash ('/'), 'R', carriage-return and linefeed.
> I don't know exactly what the next few boards are, though I know Matrox made
> video boards for a variety of systems (DEC and S100 at least) and a QRGB is
> some sort of framestore and QVAF is a digitiser, I think.  The Dataram board
> probably is memory, especially if densely packed with an array of chips.
>  The chips numbers should tell us.
> M7941 is a DRV-11 parallel interface, which might have been used for a
> printer or simply for some other digital I/O to/from another device. M7555
> is an RQDX3 MSCP disk controller, which interfaces via a breakout board to a
> dual floppy drive and/or one or more ST412-style hard drives.  Are there
> disks and cables in the system?

Yes, a cable leads from the M7941 to the front of the box, which has
the aforementioned RD54 disk and a 5.25" floppy drive.

> Thinking of that, what type of box is this in?  What does the front panel
> look like?  Jerome suggested it might be a BA23, but this mixture of cards
> suggests to me that it might just as well be a system that was upgraded from
> something older, and that it could be a BA11S or BA11N.

It's definitely a BA23.

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