[sokukodo]

I'd always "heard" that one should never completely shut down a computer, that the constant cooling/ re-heating contributes to the degradation of the CPU.
But I've been thinking (again) with dual processors in the G5, and the heat generated (CPU A: 142.81 F; CPU B: 149.92 F) on the highest setting, would it be prudent to shut the system down at night and give these babies a rest? Does it really matter? The only downside is that my number crunching activity would have to cease for at least 8 hrs a day

[MORT A POTTY]

it probably won't matter either way. the system will likely be obsolete before the CPUs ever die anyway

[sokukodo]

Thanks, Mort. Good ... the computer stays on (go Team Mac OS X)!

[Big Mac]

I have never heard any such thing. Components don't suffer damage from cooling and heating cycles. G5s are designed to be dynamically cooled by variable speed fans. Sleep mode in modern Macs shuts the fans and most everything else down. Finally, the temperature of your computer is altered by varying ambient temperatures. The thing that people do often say is that continual spinning up of hard drives by power cycles can shorten drive life, but I really have to doubt that.

[Maflynn]

I don't buy into the theory that turning them on and off shortens their lifespan.
At work we have some pretty old machines and they seem to work even though they get shut down every night. If left on the hard drive keeps spinning and that will produce wear and tear since its a mechanical devices running non stop.


Mike

[OreoCookie]

All computers sold by Apple are designed so they can be run 24 h/day. Period. It is very hard to measure aging caused by running the machine and aging that occurs even when the machine is off (e. g. the capacitors in your computer will age no matter if the machine is on or off). Components like harddrives and fans are also designed to withstand heavy-duty operation.

And also: a computer is a tool. You can and should use it as a tool should be used. (BTW, a computer's lifespan is 2-4 years, so you shouldn't worry too much anyway.)

[sokukodo]

Thanks for all the input, guys ... my mind is once more at ease.

[tooki]

In pure theory, thermal stress can result from power cycling. Perhaps this really makes a difference with systems that get extremely hot, or in particularly cold environments.

In practice, I think it's hogwash. Turn off your computer when you want, put it to sleep when you want, or leave it on when you want. It's not gonna make any perceptible difference.

tooki

[Eriamjh]

Actually, thermal stress is induced with any heating and cooling cycle. The faster the cycle, the quicker the stress is induced. This is called "thermal shock".

The CPU is fine. It's the mechanical connections that suffer from thermal shock. In your computer there are thousands or millions of mechanical connectons: solder joints.

Everything has a coefficient of expansion, and some things expand and contract at different rates or ratios. Items that expand a lot tend to break connections with things that expand very little.

In the automotive world, thermal shock is ususally from -40C to 85C or the opposite. In the computer world, its usually from 50F to 95F or even less.

So thermal cycling can kill your computer, but odds are it won't any time soon.

Worry not. Let your OSX machine sleep instead of shutting it down or leaving it one all the time. Sleep saves energy without the time wasted powering up all the way.

[tooki]

Well, the temp range you list is maybe true in Toronto, but it sure doesn't reach -40 degrees in most of the world.

As for computers, your upper range is way too low: my PowerBook routinely reaches 140 degrees F.

tooki

[SierraDragon]

Originally posted by Maflynn:
I don't buy into the theory that turning them on and off shortens their lifespan.
At work we have some pretty old machines and they seem to work even though they get shut down every night. If left on the hard drive keeps spinning and that will produce wear and tear since its a mechanical devices running non stop.

Mike

Not typically true. Hard drives normally are scheduled to spin down after some finite period of inactivity, e.g. one hour, ten minutes or whatever.