> Bill Pechter <pechter_at_pechter.dyndns.org> wrote:
> > I showed him the 11/780 design and layout and diags and he walked me
> > over to the HP mini. One slick piece of hardware. The boards were
> > cabled together neatly with one over the edge cable. All the traces
> > were gold plated and it was a pretty sight.
> >
> > He said HP stood for one thing "High Priced." But he was right about
> > the quality for the price. First rate mechanicals.
>
> Actually, DEC used over-the-edge cabling on an early minicomputer, and
> abandoned it because it was LESS reliable than backplane connection,
> and also made the machines much harder to service.
>
> Reference: _Computer Engineering: A DEC View of Hardware Systems Design_
A great book... but wrong on this one.
The hp stuff had one over the edge interconnect cable of less than 10
inches.
The DEC 11/40 (45,50,55,70, etc) in the BA11-F cabinet (the worst
offender) had about 1/3 to 3/4 of an inch of ribbon cables (thickness)
running through the cable trough an often popping off the Berg connector
at the top of the Hex, Quad or Dual board (most had no locking ears on
the connector. Yup, the backplane is more reliable as over the top
connectors, but between board cables (RH11, RH70, Cache, etc) were my
biggest pain in the _at_#$%^ at DEC). The 11/780 was a lot better with the
exception of the lousy SBI cables that were failure prone and a bitch to
troubleshoot.
The only thing worse was the annoying cables on the back of the 11/750
that were not enclosed at all... I remember the failures of an Emulex Pertec
9 track tape controller which had it's data connector to the backpanel work
loose on about 4 bits and happily wrote garbage to the tape while the
control lines worked merrily along. And the Unix system didn't know the
difference for 6 months until a drive died (read after write at the head
is NOT data verification folks).
DEC made great CPU's, decent busses and I/O boards but LOUSY CABLE
layouts (including the 11/730).
Bill
---
bpechter_at_shell.monmouth.com|pechter_at_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.
Received on Mon Nov 22 1999 - 16:05:23 GMT