From: sheldon@iastate.edu (Steve Sheldon)
Subject: Re: Leaving machine on 24hrs??
Organization: Iowa State University, Ames IA
Distribution: usa
Date: Tue, 15 Dec 1992 16:43:42 GMT

In <2B2D2A03.23733@news.service.uci.edu> eapu168@orion.oac.uci.edu (Lee Furnival) writes:

>I am in the process of advising someone in the purchase of a new pc and
>have a question regarding extending the life of the chips.  We will be
>getting a clone 486DX-33.  There are 2 cooling fans in a mid-tower case
>and I am going to install a fan/heatsink on the CPU.  Question:

 From what I've found, 2 cooling fans in a 486DX33 is more than enough.
Actually with a case with proper cooling, like a tower case usually has,
one fan is enough for a 33 Mhz chip.  The 50 Mhz might need a bit more
cooling, it all depends, or if you're filling the case with cards, 
drives, and other heat producing stuff.

 I asked a knowledgeable EE(my father :) about judging whether chips are
too hot.  Basically he said, while you can take all kinds of measurements with
temperature probes, etc, the easiest way to do field testing is your finger.
If you can't hold your finger against the chip for longer than 10 seconds
or so, the chip is too hot, and needs a heatsink.  Simple, and unscientific,
but probably fairly useful for judging long term reliability.

 Also, turning off the turbo switch will run the chip cooler.  Obviously
you'd do this if you left the computer sitting overnight not in use, or
something like that.

 Anyway...

>	Should the system be left on 24 hours a day?

>I know many UNIX freaks who leave their Suns and NeXTs and Macs on 24 hours
>a day and they say that it is better than turning the system on and off every
>day.  Is this true?  Also, we will be getting a 17" digital monitor.  Is it
>acceptable for that to be left on as well assuming we screen-save?  While the 
>logic of leaving the systems turned on has been explained to me from the
>standpoint of less stress on the chips, what about the hard drive?  Will I
>be testing the bounds of "MTBF" ratings by leaving everything on?

 Tradeoffs.  For Unix systems I think it's mainly a matter of convienience,
as shutting down and starting up takes time and is sometimes a pain.

 As far as MTBF... You're more likely to have the machine hit by a disaster.
Whether that be lightning, or somebody tripping over the cord, and having the
moving harddrive drop 3 feet to the ground. (not good, and testing the
true bounds of reliability), or other stupid tricks.

 One other consideration, especially with monitors with high voltage.  As
these things age, things go wrong.  Dust get's in them, etc.

 In our lab here, I've had two monitors literally blow up in smoke.  They
started crackling and popping, and smoke came out the top.  I unplugged
them immediately, but there is a potential for a fire to start.

 I've heard several stories of audio amplifiers left on overnight shorting
out and starting speakers on fire.

 In conclusion:

 Turn the monitor off when not in use for more than a couple hours.  A
screen saver isn't going to help it much, because screen burn-in is the
least of your problems.

 The computer.  I'd go either way.  Leaving it on is really just a matter
of convienience.  Turning it off everyday isn't going to shorten it's
lifespan. Turning it on and off repeatedly every five minutes, might,
but not once a day.


>Any info appreciated, and e-mailed info appreciated even more...

>Thanks,
>Lee Furnival
>eapu168@orion.oac.uci.edu
>eel@silverblue.fac.cs.cmu.edu

-- 
sheldon@iastate.edu                Steve Sheldon
This space left intentionally      ICSS Resource Facility
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