Newsgroups: comp.sys.ibm.pc.misc
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!quimby
From: quimby@madoka.its.rpi.edu (Tom Stewart)
Subject: Re: leaving machine on all the time?
Message-ID: <1b0f4#-@rpi.edu>
Nntp-Posting-Host: madoka.its.rpi.edu
References: <25156@hydra.gatech.EDU> <1991Mar28.203040.10490@cbnewsc.att.com>
Date: 30 Mar 91 05:40:53 GMT
Lines: 58

>I TOTALLY DISAGREE will all of this fear of turning computers (electronics)
>off when NOT IN USE for extended periods, including OVER NIGHT.

I don't think it's a fear, more than an understanding that leaving 
the machine on may very well prolong it's life.  (Exception:  If you
have a Seagate drive, fear of turn-off is probably appropriate.)

>It appears a little knowledge is a dangerous thing, the kind of stress that
>occurs to electronic devices during turn on/off cycles and warm up/cool down
>periods is insignificant for the typical user.  We do stress testing on our
>products that goes way beyond normal to OVER-stress the design and look for
>the weaknesses and eliminate them.

That power and thermal cycling are standard reliability tests doesn't
speak well of using power and thermal cycling as standard operating
procedure.

>Do you keep your auto engine ON when you are not using it (it also heats UP
>and cools down). DO you leave lights ON (if you pay the bills).  etc.

Do you turn off your watch at night, or alarm clock during the day?  
Both devices have a lot more in common with a computer than a computer
does with either a light bulb, gasoline engine, or power saw.

>Apply common sense.  Hard drives have mechanical parts that DO wear out
>with use.  In additional, a power line spike may damage your unprotected
>computer.  Certainly more ON time will increase your risk and reduce the
>life of mechanical parts.  Do not forget that many electrical parts also
>have wear-out (e.g. electrolytic capacitors).

Power surges usually aren't kind enough to wait until you turn
the machine off.  Small surges tend to occur during daylight, when
people are playing with the airconditioners and arc welders.  

Cerainly one of the most likely to fail devices in a typical computer
is the hard drive, which is mechanical.  As to whether this device
will last longer if run continously or cycled every few hours -- it
depends on the drive.  Some drives don't like to spin up, or down,
others don't mind, but crash once in a while.  Every mechanical or
electrical system that I know of experiences more stress on startup
than during normal operation -- high inrush currents, thermal stress,
starting friction, etc.  Often systems have to be built into products
to reduce these stresses -- inrush limiters, protecting diodes and
surge supressors, dry sump oil systems, etc.  
  
If you'd like to stretch the life span of your computer, keep it cool,
and clean.  It's probably safe to ignore arguments on both sides as
to turning it off for breaks or overnight, but it's also probably
a good idea to turn the monitor off, if for no other reason than the
reduction of the fire hazard.  Me, I'll continue to keep my machine
up, and advise our customers to do the same.  It's been our experience
that constinously operating machines don't fail as frequently as the
9 to 5ers.
 
Quimby
  
(mailer disfunctional, replies to: quimby@mts.rpi.edu, quimby@rpitsmts.bitnet)
 
