KD-11F (11/03) in a BA11-N??

[Pete Turnbull]

On 07/01/2009 01:27, Bob Armstrong wrote:
>   I have a BA11-N chassis that says "11/03-L" on the front, and the
> backplane in it is an H9273-A.   I want to get this to work with a 11/03 CPU
> (a real KD11-F M7264) but there's something strange about this backplane
> that I can't figure out.
> 
>   The boards I'm using are the M7264, an M8044 (MSV11-D), M8017 (DLV11-E)
> and a BDV11.  In a small, 4 slot 11/03 chassis (a BA11-S, I think)

No, that'll be a BA11-M, with a H9270 18-bit 4 x 4 serpentine backplane. 
  BA11-S is a box with a H9276 9-slot 22-bit backplane, used for a 
PDP-11/23plus.

> all these
> boards work fine together, however in the BA-11N there's no joy.  It powers
> up, but the processor appears to halt immediately - it never executes the
> BDV11 bootstrap.
> 
>   But, if I replace the 11/03 CPU in the BA11-N with a 11/23 CPU card, then
> everything is fine.  So the 11/03 works fine in the BA11-S but not in the
> BA11-N, and the 11/23 works fine in the BA11-N.
> 
>   It seems fairly likely that there's some kind 16/18/22 bit addressing
> issue here, but what's the fix?  It must have been possible to use the
> KD11-F in the BA11-N, given the 11/03-L designation.  

Not necessarily, the BA11-N was designed when the dual-height LSI-11/2 
(M7270, KD11-H) was used, and then was also used for the 11/23 systems.

The issue is not the number of address bits, which won't matter at all. 
  It's that your H9273 backplane is set up for an 11/23 and won't have 
W2 and W3 inserted, but they need to be for a quad-height M7264 (and 
only for that board AFAIR, don't insert them if you use a quad-height 
KDF11-B).

>   FWIW, the backplane has not been field upgraded with wire wrap to add the
> extra address bits.  In fact, the H9273-A doesn't even have wire wrap pins
> at all - the pins are all cut off right at PCB level.  Is this the standard
> backplane for a 11/03-L system?   I'm wondering if at some time maybe the
> whole backplane was replaced with a newer one.

No, that's normal for almost all Q-bus backplanes, and you do have the 
normal backplane for a BA11-N.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York