PDP 11/23 PLUS system for sale

[Allison]

>
>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
>
>>>>>> "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

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