BDV11 ROM programs?

Pete Turnbull pete at
Thu Dec 11 17:05:30 CST 2014

On 11/12/2014 17:58, Noel Chiappa wrote:
> Does anyone know of anything that documents the contents of the various BDV11
> ROMs? In particular, I'm interested in learning what the various halt
> locations imply.

Well, the binary images are on my website at

The binary files are 23-045E2.bin and 23-046E2.bin in that directory.

That would save you trying to write something to extract the contents 
from the system; you are aware that although there's 2KW of code in 
there, it's accessed through a 256-byte (128 word) window in Bank 8 
which has to be programmed via the PCR?

There are 18 error halts, listed in the BDV11 manual, which I expect is 
on bitsavers, and on pp107-108 of the PDP-11 Microcomputer Interfaces 
Handbook 1980.

> There seem to be two different ROM sets; 23-046E2/23-045E2, which seem to be
> an earlier set, as they only understand 56KB of memory; and a later set,
> SG8326-339E2 and SG8330-340E2 (which might not be DEC standard, the numbers on
> them are 'odd' - although they might be 23-339E2/23-340E2, the boot ROMs from
> the 11/23+), which understand up to 4MB of memory.

They almost certainly are.  23-045E2/23-046E2 are the BDV11 ROMs (there 
was only ever that one set in public).  SG8326 and SG8330 look like date 
codes, and 1983 would be about right for partway through the life of an 
11/23+.  Also 23-339E2/23-340E2 are indeed the standard 11/23+ 
bootstrap/diagnostic ROMs.  Perhaps someone's made a "backup copy" and 
used it as an upgrade, because although DEC did use EPROMs they put 
standard part numbers on them.

If you want to compare, 23-339E2.bin and 23-340E2.bin are also on my 

The 25 error halts for the 11/23+ are listed on pp 611-613 of the 
Microcomputers and Memories Handbook 1982, and also on pp 47-49 of the 
PDP-11/23-PLUS System Manual (EK-1T23B-OP-001).

> (Interestingly, the latter set are on Intel D2716s, EPROMs, unlike the earlier
> ones, which are plain PROMs.)

You've already discovered, I imagine, that there are gazillions of ways 
to set up and use the sockets on a BDV11, and one way is to allow the 
use of EPROMs in the main socket pair.  The settings are in the BDV11 
manual - which I have, but can't get to right now, though it's probably 
on bitsavers as I mentioned above - and also on pages 86-113 of the 
PDP-11 Microcomputer Interfaces Handbook 1980.  Specifically, W5-W8 and 
W13 (page 98) set the ROM/EPROM type for the main pair of sockets.  For 
2716 EPROMs, they should be W5,W6,W8 removed and W7,W13 inserted. 
That's actually the same as one of the two types of mask ROMs; the other 
type uses W5 inserted and W13 removed.  The difference is due to 
opposite polarity of one of the three chip selects (CS3).

You should also look up the functions of the switches, as they set the 
bootstrap type, and the LEDs as they tell you something about what's 
being tested during boot and what errors if it fails.


Pete Turnbull

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