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From: jc58+@andrew.cmu.edu (Johnny J. Chin)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Leave the PC on vs. Power it off daily?
Message-ID: <8axQEga00VY642bGAb@andrew.cmu.edu>
Date: 18 Sep 90 06:52:28 GMT
Organization: Carnegie Mellon, Pittsburgh, PA
Lines: 36

Power On and Off a PC puts the most wear on your hard drives.  The spin down
and spin up of the platters causes the spindle to wear out.  Leaving the
system on all the time allows the spindle to spin with less friction, thus
less wear.

As for the components of the computer (ie. the silicon chips), the power spikes
induced by a power on decrease its life (this is more so with the denser VLSI
chips because of the narrower width of the electrical lines).

The problem with leaving PCs on is the load that is induced on the transformers
out in the street.  PCs use a switching power supply; what this means is that
the power supply switches "on and off" 60 cycles per second.  This does NOT
mean that the PC turns on and off 60 times every second.  Because of this
"on and off" of the switching power supply, a larger load is demanded from
the transformers (due to lots of small sudden demands for power).

Ultimately, what should you do?  Leave it on or turn if off daily?
Well, my suggestion is ... if you use the computer a lot (ie. more than 10
hours a day) and use the hard drive a lot during this time (ie. not sitting
in your word processor all day, but doing reads/writes), I would leave it on.
Otherwise, I'd turn them off at night.  I use my PC about 8-10 hours a day
with about a lot of reading/writing; I still turn off my PC when I don't plan
on using it for several hours.  Besides, it saves on the electric bill and
lowers the chances of getting spikes and brown-outs.

Remember, this is my opinion only.
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Disclaimer:   The views expressed herein are STRICTLY my own, and not CMU's.