2 Feb
2002
2 Feb
'02
8:59 a.m.
--- Bill Pechter <pechter(a)bg-tc-ppp726.monmouth.com> wrote:
The actual loads were the same. It was that there were two possibilities
for where to get each of the Unibus signals, circa 1981, depending on
exactly what backplane you were looking at. I wasn't at the company
at the time, but the engineer saw one example of the Unibus and based
the board on it. He chose wrong.
Speaking of
CPU and Unibus together, there are a few machines that
follow their own rules - the Unibus slots in a 11/730 and 11/725
(and one model of PDP-11) are *not* wired identically to the slots
in a DD11DK....
It's been a long time -- I was trained on the 11/7xx series at DEC in
'85 or so and I don't remember any special things about their Unibus as
far as bus loads, power or signals. IIRC they 11/730 and 11/725 were pre-cut for DMA
devices and had to have
special dual-width Unibus grant cards in place if the slots were empty.
Yes. We provided instructions for how to cut and replace the NPR
jumper when installing our board because most people didn't have
the dual-height grant cards. We used to ship one with every board.
They cost us $18.75 each (for the model that had no silk-screen
legend, just copper). I don't know what the "Grantasaurus" cards
cost us. Those haven't been made since before 1984.
IIRC, again it was because ot the tightness of the
packaging of these
slots, anything in the Unibus expansion cabinets was standard.
They were a little odd due to the packaging. Speaking of which, when
I said the "11/730", I meant the model that could take the RB80 at the
bottom of the cabinet, the CPU in the middle and the RL02 at the top,
the 11/730-Z. I do not know if they used the same backplane in the
other style of 11/730, the one with the BA-11-style box at the top
of the rack and lots of empty space underneath for cables, etc (like
an 11/24 or 8200). We never had that style, but I kinda always wanted
one because it would have been easier to work on. Wish I still had
my 11/725. :-(
-ethan
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