22 Nov
1999
22 Nov
'99
11:53 a.m.
I'm not talking about I/O cables that are many
feet long between a card and
an external device, nor cables under two inches between just a few boards
in the same backplane.
I'm talking about using over-the-edge cabling for bussing signals between
many cards in the same backplane, and that's what I was referring to the
book about. This was done in the PDP-6, IIRC, and they decided that it
was a maintenance nightmare. If HP somehow made this scheme work reliably
and somehow kept it from being a headache to troubleshoot, I'd be interested
in hearing how they did it. Obviously HP must not have thought it was
a particularly great technique, since they generally aren't using it today.
The answer is get the machine down to 6 boards in less than a foot of
length with one aproximately 50 pin cable.
Worked fine.
They built a nice clean maintainable box. The PDP6 was a transistorized
machine with much more cables needed than the HP mini.
We're talking an early to mid 70's design vs. a late 70's to early 80's
design. Apples and oranges. The hp looked a lot cleaner than the
11/44 or 11/70 and seemed much smaller in number of boards and simpler
in layout of signals.
Bill
---
bpechter@shell.monmouth.com|pechter@pechter.dyndns.org
Three things never anger: First, the one who runs your DEC,
The one who does Field Service and the one who signs your check.