Best name for PDP-11/05-10

Mattis Lind mattislind at
Fri Feb 26 09:05:07 CST 2016

2016-02-26 15:04 GMT+01:00 Noel Chiappa <jnc at>:

>     > From: Mattis Lind
>     > The NC is in the BA11-D 10 1/2 inch box. It uses the H750 PSU.
> Odd. I have an -11/10 in a 10-1/2 box with an H750; the metal plate on the
> back of the box just says "PDP 11-10" (well, the '-' is actually a dot, at
> the level of the '-'). No 'NC'. I wonder if that's a configuration
> designator, not a model?
Min doesn't say NC / ND either.

I have a physical tech manual (which is not the same as the one at
bitsavers) and engineering drawings (which is the same as the one at

I should probably scan that tech manual if someone hasn't done it already.
Compared to the one at bitsavers it for example include an appendix
 related to some minor modifications that had been done to the CPU board

> {At this point, IRL, I did a whole lot of reading and looking.}
> I looked in some old PDP-11/05-10 price lists... (More "11/21"s... :-), and
> did find some -11/05 models with pretty large alphabetic model designators,
> e.g. "11/05-LB", but no "11/10-NC". However, the "Options and Modules List"
> online from June, 1974 _does_ list the "11/10-NC" - it describes it as
> "KD11-B, BA-11DC 10.5 INCH BOX, MM11-L, KY11-JE, CONFIG 4, 115V". There's
> also an "11/05-NC", the same except for a "KY11-JD" (that must be for the
> different number printed on the faceplate). No idea what the "CONFIG 4"
> means...
> However, the real victory came when looking in my just-acquired copy of
> DEC-11-H05AA-B-D.pdf. I see it also includes a "DEC-11-H05AA-B-D Supplement
> 1", which is the "PDP-11/05, 11/10 10 1/2 inch mounting box and power
> system"
> - and that _does_ describe the NC/ND (120V/240V). And those have a slightly
> different backplane (below) from the ones described in DEC-11-H05AA-A-D; so
> that's a fourth model of -11/05-10 backplane - and it does differentiate
> the -11/05N-10N (as I will call them) from the others.
>     > I have three machines with three different backplanes. One 11/05-NC,
>     > one 11/10 in 5.25 inch box and one 11/05-S in BA11-K.

I was lying a little bit when saying NC. Actually it is the ND model for
obvious reasons. But the difference is subtle. Just the power input module.

> What kind of backplane does the second one have; one of the 2xMM11-L CPU
> backplanes (one with, and one without, an SPC slot), or the 1xMM11-L?

It is the 1xMM11-L type of backplane. But the system came with an extra
5.25 inch memory box. Identical to the CPU but different backplane for
three more MM11-L modules

>     > NC can have two MM11-L. No SPC slots.
> Got it. I was very confused, because the 11/05-10 manual (DEC-11-H05AA-A-D)
> says that the 2xMM11-L backplane has one SPC slot (the last one, IIRC).
> However, as noted, the -11/05N-10N apparently has a different backplane, to
> accomodate the M9970 dual console serial line connector card. (That
> backplane
> isn't documented in the DEC-11-H05AA-A-D -11/05-10 manual I'd been looking
> at
> - that manual doesn't show a space on the 2xMM11-L backplane for that
> card).
> However, the later "PDP-11/05, 11/10 10 1/2 inch mounting box and power
> system" manual _does_ describe it; and in adding a slot for the M9970, they
> lost the SPC slot in the 2xMM11-L backplane.
> So I guess that's the one you're talking about here?

It is the latter with space for the M9970, DF11 and KM11 instead of an SPC.
The bitsavers document above has the backplane on page 19.

>     > From: Bill Degnan
>     > The more useful box is the S model because the more standard
> enclosure
>     > can be used for testing other UNIBUS cards more easily or than parity
>     > RAM.
> ?? How is is better? The BA11-D box will hold hex cards? Or are the SPC
> slots
> in the 11/05-10S backplane MUD slots? Or is it just that the BA11-K will
> hold
> DD11-C/D backplanes, with MUD slots? (I don't know if there are any MUD
> backplanes that go into the BA11-D - at least without a hand-mod to the
> power
> connector.)
>         Noel


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