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From: oyster@uwmacc.UUCP
Newsgroups: comp.org.decus
Subject: Re: Noisy terminal lines
Message-ID: <1300@uwmacc.UUCP>
Date: Fri, 27-Mar-87 10:26:35 EST
Article-I.D.: uwmacc.1300
Posted: Fri Mar 27 10:26:35 1987
Date-Received: Sat, 28-Mar-87 12:51:45 EST
References: <8811@decwrl.DEC.COM> <1592@tekigm2.TEK.COM>
Reply-To: oyster@unix.macc.wisc.edu.UUCP (Vicarious Oyster)
Distribution: na
Organization: UW-Madison Academic Computer Center
Lines: 35

In article <1592@tekigm2.TEK.COM> jimb@tekigm2.UUCP (Jim Boland) writes:
> >If there isn't any idle time,
>>the problem is most likely a terminal line which is passing transmit
>>data to receive data, using lots of CPU time echoing the same thing
>>over and over. 
...
>We traced it down to a noisy terminal line which had nothing connected at the
>other end.  Disconnecting unused terminal lines solved the problem.
>
>There was a software routine printed in DEC PROFESSIONAL(I believe) in
>Fall of 85 that checks for terminal activity.  I don't remember which
>issue and my issues don't go back prior to Dec 1985.  I remember the
>article,though, and we tried the program.  It helped to find our problem.

  That's the February 1986 issue (Volume 5, Number 2).  The basic algorithm
is:
   1) Examine KB; if logged in, go to next KB, else continue.
   2) Determine speed setting of KB.
   3) Set speed to zero.
   4) Time some arbitrary calculation & display result.
   5) Set speed back to normal.
   6) Repeat calculation & display results
   7) Next KB

   The author printed results of a sample run where two terminals were causing
problems; they ran the calculation at ~60% of the "zero speed."
--

 - Joel Plutchak, ex-RSTS system manager
   uucp: {allegra,ihnp4,seismo}!uwvax!uwmacc!oyster
   ARPA: oyster@unix.macc.wisc.edu
   BITNET: plutchak@wiscmacc

Disclaimer:
   If subpoenaed, the U of W will disavow all knowledge of my actions.