13 Jun
2021
13 Jun
'21
1:44 p.m.
I am working on the first of my two 11/05s. Interestingly, it has the early version M7261E
Control
Logic & Microprogram board and the later version M7260 Data Paths board (with circular
baud rate
selector switch) as described in:
http://gunkies.org/wiki/KD11-B_CPU
From the description there, 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 have a couple different drawing sets for the 11/05 and while some have the matching
M7260
schematic, only the GT40 drawings (I found on bitsavers) has the M7261E schematic:
http://www.bitsavers.org/pdf/dec/graphics/VT11/GT40_Graphic_Terminal_Engine…
The GT40 drawings has the PROM listings and related, so I am hoping that they match what
is in the
two boards.
Presently, the machine sometimes runs relatively well and other times it does not. It does
have bit
1 stuck ON in memory, but that should be a relatively simple task to diagnose as it is
not
intermittent. When the machine is "working" I am able to deposit 0777 at 0100
and run. When running
this simple program, I've experimented with flexing the boards and such, so it
doesn't seem like an
obvious poor connection, but that remains to be seen.
The machine is a configuration #2 model (as described in the "gunkies" site) and
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?
Thanks much to those who have provided details and documents on the web, they have already
been of
great value and will most certainly continue to be a resource in the future.
More updates in the future...
--tom
On 5/6/16 5:32 PM, Noel Chiappa wrote:
From: Mattis
Lind
Thanks Noel for sorting this out.
Eh, de nada. But thank you.
> I wonder if the ucode in the two versions is
identical? The uROM chip
> numbers should give it, (if they are the same on both versions, albeit
> in different locations on the board), but I have yet to check. Does
> anyone happen to know?
OK, so the situation here is pretty complicated. To start with / make things
worse, that CPU uses lots of PROMs. Lots and lots and lots and lots of PROMs.
For the data paths board (M7260), both major versions appear to contain the
same PROMs (going by the DEC part numbers), but the chip location (Exx)
numbers are all different.
For the control board (M7261), the C, E ('early' version) and F ('late'
version) etch revisions each contain mostly the same PROMs, but apparently
with slight differences between the sets of PROMs in each (as reflected in
different DEC part numbers). For details see:
http://gunkies.org/wiki/PDP-11/05#Control_PROMs
to which I have just added all the gory details.
As to getting the contents of all of them dumped in machine-readable form -
oi vey!
> on the earlier version (prints for that
version are in the GT40 prints
> online
It turns out that I have hard-copy prints for the "C" etch revision of the
M7261, which do not yet appear to be online; the GT40 prints have the "E"
etch revision.
I will scan the pages for that revision of the board, and put them up 'soon'.
(I'm not doing the whole print set, it's about 1" thick, and most of them
are
for other things anyway, like MM11-L memory, etc.)
Noel