PDP-11/05 (was: PDP-11/05 microcode dump?)

[Josh Dersch]

On Mon, Jun 14, 2021 at 10:34 PM Tom Uban via cctalk <cctalk at classiccmp.org>
wrote:

> On 6/14/21 3:39 PM, Noel Chiappa via cctalk wrote:
> >     > From: Tom Uban
> >
> >     > it has the early version M7261E Control Logic & Microprogram board
> and
> >     > the later version M7260 Data Paths board
> >
> > Ah, I'm glad someone found all that stuff I wrote up there useful. As
> always,
> > I _think_ I got it all transcribed correctly, but do be on the lookout
> for
> > errors!
> I most certainly did - thank you for creating it!
> >     > it seems like an older/newer combination, but maybe that was
> common. I
> >     > would not have guessed that the four possible combinations would
> all
> >     > work together, but maybe they do?
> >
> > I honestly don't know. As far as I can tell, the DEC documentation
> doesn't
> > even _mention_ the two different board generations; perhaps a sign that
> they
> > are functionally interchangeable? (Although even the section on baud
> rate, in
> > both DEC-11-HKDBB-A-D and EK-KD11B-MM-001, 4.11, doesn't even mention the
> > early board. So maybe the manual just ignores the earlier version
> completely?)
> >
> > I don't have an /05 up and running at the moment, or I'd check all 4 and
> see
> > if they all work.
> >
> >     > Presently, the machine sometimes runs relatively well and other
> times
> >     > it does not.
> >
> > What are the failure symptoms? (It's almost certainly going to take a
> 'scope
> > to fix it; I expect you have one?)
> I have KM11s, a scope, a logic analyzer, a unibone, shiresoft unibus
> analyzer, etc.
> No shortage of gear, just a shortage of time.
> > I'd start by monitoring the CPU clock, and make sure it's running when
> the
> > failure happens. (Note that the front console is handled by the
> microcode, so
> > if the microcode isn't running, the machine will be totally dead.
> > EK-KD11B-MM-001 has a good description of how that works.)
> I think I checked the clock when I started this project a while back, but
> I will
> check it again. Unfortunately, I haven't figured out how to provoke two
> states,
> but it mostly picks the completely dysfunctional state, so I'll look at
> the clock.
> >     > my initial messing with KM11 boards, reveals that I can step the
> >     > microcode with a KM11 in either the #1 or #2 position, but when two
> >     > KM11s are installed at the same time, they do not function properly
> >     > together. Is this expected or do I have an issue there too?
> >
> > Not sure. EK-KD11B-MM-001 (available at:
> >
> >   http://www.bitsavers.org/pdf/dec/pdp11/1105/EK-KD11B-MM-001_Jan75.pdf
> >
> > and definitely something you need) says, at pg. 5-6 "KM11 switches have
> the
> > same function in slots KM-1 and KM-2", and on 5-7 "permits the user who
> has
> > only one KM11 to plug into either KM-1 or KM-2".
> >
> > So that _sounds_ like you should be able to plug two in together. The
> first
> > indicates that the switches, the only input to the KD11-B from the KM11,
> are
> > wired in parallel, and the only other thing on the KM11 are the lights,
> > outputs. And why mention "user who has only one KM11", if having two is
> no
> > use because one can't use two at once?
> I've read that doc, but did not come away with the impression that both
> can be used at the same time or not.
>

Just to provide some real-world data, I used a pair of KM11's to debug my
11/05, see the picture here:

http://yahozna.dyndns.org/scratch/1105-debug.jpg

They worked fine.  (These are clones, from Guy Sotomayor's kit.)  I can
verify tonight whether I have the earlier or later rev CPU set, if that
helps.

- Josh