15 Jun
2005
15 Jun
'05
12:31 p.m.
Subject: RE: PDP 11/23 PLUS system for sale
From: Paul Koning <pkoning at equallogic.com>
Date: Wed, 15 Jun 2005 14:28:02 -0400
To: cctalk at classiccmp.org
No they _could_ corrupt data, not they did all the time. The differnce
was the error rate was not what DEC wanted for transactions. The VAX
people put pressure to not have to test the data as LAVCs (Local Area
VAX Clusters) were popular to a point and required a very high level
of data (code!) integrety. The frequency of the failure was related
to the traffic level on the local loop.
The second level of that was plain product improvement. The DEQNA
was a dense board with a low MTBF (errors excluded) and field support
and board costs were high. Replacement (supported [aka endorsed] by
the VAX folks) was a desireable thing if the new card was more robust
[higher MTBF and fewer "bugs"].
I was part of the uVAX side of things as the products I was involved with
(LPS40 and LPS20 network printers) used an embedded microVAX and the
LPS40 inparticular was a complete BA23 sans disks and netbooted from
host VAX. It was "interesting" string of events. Such was the fun
of being there.
Allison
>>>> "Allison" == Allison
<ajp166 at bellatlantic.net> writes:
Allison> Actually depending on OS and general usage the critical
Allison> factor for the DEQNA was not rev but, is it functional at
Allison> all? Most of the DEQNAs I've touched and used either worked
Allison> or were dead, rev was a minor issue save for certain OS
Allison> support issues. One of the REV issues was that the more
Allison> reworked versions tended to have more failures (IE plain old
Allison> dead) resulting from greater amounts of handeling and
Allison> use/abuse. For Q-bus 11s the DEQNA was an acceptable
Allison> device.
From what I remember (very blurry now) DEQNAs were
known to corrupt
data. That was very obvious on VAXclusters, which is why VMS
eventually took them off the supported device list permanently. But
it's an issue for any application (except, *maybe*, when running TCP
since the TCP layer checksum may help -- or may not, it's not that
strong...). That applies just as much for PDP11s.
paul