29 Jul
2015
29 Jul
'15
10:08 a.m.
If you were following Joerg Hoppe's recent PC05 auction on eBay, you might have
noticed that his system had an M705 in the backplane where I would have expected an M7050.
This is the way he received it and the restored unit works as it should.
Clearly the cards are similar but different but are they interchangeable? Would the
backplane wiring be different and if so where would this be recorded?
My copy of the PC04/05 maintenance manual (DEC-00-PCOA-D(1)) makes no mention of the M705
in this location. The PC04/05 print set on Bitsavers has the M705 on the module
utilization list (p45) but crossed out with no reference notes. There is an ECO list on
the sheet, showing PC05 ECO's 3, 16 and 30 but no specifics. Is there an available ECO
log that would cover these notes?
Then there's the K303, but that's another story...
Jack
29 Jul
29 Jul
10:28 a.m.
On 2015-07-29 19:08, Jack Rubin wrote:
If you were following Joerg Hoppe's recent PC05
auction on eBay, you might have noticed that his system had an M705 in the backplane where
I would have expected an M7050. This is the way he received it and the restored unit works
as it should.
Clearly the cards are similar but different but are they interchangeable? Would the
backplane wiring be different and if so where would this be recorded?
My copy of the PC04/05 maintenance manual (DEC-00-PCOA-D(1)) makes no mention of the M705
in this location. The PC04/05 print set on Bitsavers has the M705 on the module
utilization list (p45) but crossed out with no reference notes. There is an ECO list on
the sheet, showing PC05 ECO's 3, 16 and 30 but no specifics. Is there an available ECO
log that would cover these notes?
Then there's the K303, but that's another story...
Don't know any specifics here, but I know that DEC made improved cards
in many cases, where they added a 0 at the end of the improved card.
Examples:
M454 - M4540
M596 - M5960
M930 - M9300
There are also examples where the zero was added, and the new module
replace a set of modules that combine to implement a device.
These are PDP-11 examples, you can find even more of this on the PDP-8
side of things.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
10:51 a.m.
From: Jack Rubin: Wednesday, July 29, 2015 10:08 AM
If you were following Joerg Hoppe's recent PC05
auction on eBay, you might
have noticed that his system had an M705 in the backplane where I would have
expected an M7050. This is the way he received it and the restored unit works
as it should.
Clearly the cards are similar but different but are they interchangeable?
Would the backplane wiring be different and if so where would this be
recorded?
I don't know where to find backplane documentation, but I did at one
time diff the net-lists for some versions of M705 vs M7050. Those
results are paraphrased in
http://svn.so-much-stuff.com/svn/trunk/Eagle/projects/DEC/Mxxx/M7050/M705vs…
The gist of it seems to be that to use an M7050 in an M705 backplane,
BU1 must be high (will probably float high), and BC1 must not be grounded,
New output pins BL2, BT2, and test point AC1 should be unconnected.
A fair chance it will "just work".
Going the other way is probably more difficult, as you'd have to fake
BL2 and BT2 somehow.
Hope that helps!
Vince
11:56 a.m.
It could also be the extra "0" is for some reason intended to be
installed in an expansion chassis for the system. It is a stretch to
make this assumption, the thought occured because I know the power
supply in an expansion chassis I have is called h7420a, whereas the
main unit part number is h742a..
On Wed, Jul 29, 2015 at 1:51 PM, Vincent Slyngstad
<v.slyngstad at frontier.com> wrote:
From: Jack Rubin: Wednesday, July 29, 2015 10:08 AM
--
Bill
vintagecomputer.net
If you were following Joerg Hoppe's recent PC05 auction on eBay, you might
have noticed that his system had an M705 in the backplane where I would
have
expected an M7050. This is the way he received it and the restored unit
works
as it should.
Clearly the cards are similar but different but are they interchangeable?
Would the backplane wiring be different and if so where would this be
recorded?
I don't know where to find backplane documentation, but I did at one
time diff the net-lists for some versions of M705 vs M7050. Those
results are paraphrased in
http://svn.so-much-stuff.com/svn/trunk/Eagle/projects/DEC/Mxxx/M7050/M705vs…
The gist of it seems to be that to use an M7050 in an M705 backplane,
BU1 must be high (will probably float high), and BC1 must not be grounded,
New output pins BL2, BT2, and test point AC1 should be unconnected.
A fair chance it will "just work".
Going the other way is probably more difficult, as you'd have to fake
BL2 and BT2 somehow.
Hope that helps!
Vince 
12:06 p.m.
A lot of the early unibus boards which were 3 digit and replaced by a 4
digit were duel height boards that required a M7821 and M105 (not sure
about the numbers), and DEC built those into a quad height board and added
a "0".
On Wed, Jul 29, 2015 at 1:56 PM, william degnan <billdegnan at gmail.com>
wrote:
It could also be the extra "0" is for some
reason intended to be
installed in an expansion chassis for the system. It is a stretch to
make this assumption, the thought occured because I know the power
supply in an expansion chassis I have is called h7420a, whereas the
main unit part number is h742a..
On Wed, Jul 29, 2015 at 1:51 PM, Vincent Slyngstad
<v.slyngstad at frontier.com> wrote:
http://svn.so-much-stuff.com/svn/trunk/Eagle/projects/DEC/Mxxx/M7050/M705vs…
From: Jack Rubin: Wednesday, July 29, 2015 10:08
AM
>
> If you were following Joerg Hoppe's recent PC05 auction on eBay, you
might
> have noticed that his system had an M705 in
the backplane where I would
> have
> expected an M7050. This is the way he received it and the restored unit
> works
> as it should.
>
> Clearly the cards are similar but different but are they
interchangeable?
Would the
backplane wiring be different and if so where would this be
recorded?
I don't know where to find backplane documentation, but I did at one
time diff the net-lists for some versions of M705 vs M7050. Those
results are paraphrased in
The gist of it seems to be that to use an M7050 in an M705 backplane,
BU1 must be high (will probably float high), and BC1 must not be
grounded,
New output pins BL2, BT2, and test point AC1
should be unconnected.
A fair chance it will "just work".
Going the other way is probably more difficult, as you'd have to fake
BL2 and BT2 somehow.
Hope that helps!
Vince
--
Bill
vintagecomputer.net
30 Jul
30 Jul
4:35 a.m.
Hi,
If you were following Joerg Hoppe's recent PC05
auction on eBay, you might have noticed that his system had an M705 in the backplane where
I would have expected an M7050. This is the way he received it and the restored unit works
as it should.
Clearly the cards are similar but different but are they interchangeable? Would the
backplane wiring be different and if so where would this be recorded?
My copy of the PC04/05 maintenance manual (DEC-00-PCOA-D(1)) makes no mention of the M705
in this location. The PC04/05 print set on Bitsavers has the M705 on the module
utilization list (p45) but crossed out with no reference notes. There is an ECO list on
the sheet, showing PC05 ECO's 3, 16 and 30 but no specifics. Is there an available ECO
log that would cover these notes?
Then there's the K303, but that's another story...
While repairing I found these functional differences between M705- and
M7050-based PC05's:
http://retrocmp.com/stories/dec-pc05-papertape/240-dec-pc05-model-evolution
Differences are the generation of the reader's data clock signal
(Stepper motor position vs. feed hole pulse) and the "end of tape"
condition" (tape photo cell vs. feed hole timeout).
Joerg
3214
days inactive
3215
days old
5 comments
6 participants
participants (6)
-
billdegnan＠gmail.com -
bqt＠update.uu.se -
j＠ckrubin.us -
j_hoppe＠t-online.de -
useddec＠gmail.com -
v.slyngstad＠frontier.com