11 Jun
2001
11 Jun
'01
10:57 a.m.
I came across some M9202 "Unibus connector inverted", and I'm wondering
if anyone knows what they are used for?
-Larry LeMay
11 Jun
11 Jun
11:35 a.m.
New subject: TI SR-51 calculator operator guide
I just found my copy of the TI SR-51 calculator "Operating Guide", a small
19-page operating summary for the SR-51 calculator printed in 1974. The
calculator and full manual were donated years ago, but this guide is
available free to somebody who collects historical TI calcs.
Bruce
bkr(a)WildHareComputers.com
11:52 a.m.
Lawrence LeMay wrote:
I came across some M9202 "Unibus connector inverted", and I'm wondering
if anyone knows what they are used for?
To connect UNIBUSES, of course :)
It is used to connect two adjacent UNIBUS backplanes of a DEC PDP-11
system. They are commonly found in BA11 expansion shelves to connect
the segments of the backplane.
--
Doug Carman
pdp11(a)bellsouth.net
12:04 p.m.
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5:49 p.m.
Tony Duell wrote:
True. And it gets more sensitive as you add peripherals and increase
the total unibus (aggregate) length. Our 11/45 system, 2cpus sharing
memory, has a 5' cable btween the KB11 backplane and the first SPC.
I found out the hard way one night when that cable went bad that the
system would flat not run with either a M920 or M9202. It liked the
spare 6' cable we had on hand, though.
When I mentioned this to our field rep (Link, not DEC) I was told that
our system was "tuned" to a certain length due to its complexity and
that all unibus cables be replaced only with those of equal length.
I came across some M9202 "Unibus connector inverted", and I'm wondering
if anyone knows what they are used for?
IIRC, the M9202 is a Unibus jumper (used to connect the Unibus Out of one
backplane to Unibus In of the next) with 2' of cable folded up between
the PCBs. It thus adds a slight delay to the signals.
The are supposed to be some DEC rules about when to use M9202s and when
to use M920s (the plain Unibus jumper). My experience suggests that for
most systems you can use either jumper and it will work.
One thing you can do with the M9202 is drill out the
rivets hold it
togther. This will leave you with full-length PCBs with handles on them
linked by 2' of cable. This is ideal for bypassing a backplane (pull out
the jumpers connecting it to the ones on either side and put this
'cable' between Unibus out of the previous backplane and Unibus in of the
next). Which can be useful when you're tracing grant problems.
Good troubleshooting aid. That 5' BC11 works great for this, and long
enough to extend to the expander rack.
-tony
.... nick o
8595
days inactive
8596
days old
4 comments
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ard＠p850ug1.demon.co.uk -
bkr＠WildHareComputers.com -
lemay＠cs.umn.edu -
oliv555＠arrl.net -
pdp11＠bellsouth.net