Thread: Is this true?
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Randy B. Singer

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Location: Sacramento, California
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Originally Posted by IMACFAN15 View Post
I was reading some of the old posts on this website, and someone once had said macs were made not to be shut off. Is that true?
There is no set rule for this. No right or wrong answer.

I believe that the reason that many folks have heard that computers should be left on all the time is because the first computers (the ones that took up entire rooms) were designed to never be shut down. Personal computers don’t have anywhere near the quality of components (that is, their robustness, not how advanced they are) that those computers had. Personal computers are built to a price point. Their hard drives have a limited lifespan (rated in Mean Time Before Failure -MTBF, you can find this rating on the drive manufacturer's Web site), their switches wear out eventually, solder joints crack from heat cycling, capacitors pop from withstanding too many surges, etc. (Which is not to say that if you leave your Macintosh on all the time that it will likely fail in a short period of time. It won't. Macs are revered for their long life-spans. But less wear tends to be better than more wear. Hard drives not un-commonly fail.)

With regard to desktop Macs, the choice of shutting your computer down or leaving it on is a wash. There is no right choice. If you leave it on, your hard drive is spinning continuously, and you therefore shorten the life of the hard drive. If you turn it off you put the computer through heat cycling (hot to cold, cold to hot) and increase the chances of a cracked (i.e. cold) solder joint. The decider for some may be that you save energy by shutting down at night and waste energy by leaving your computer on.

The biggest problem with a laptop is heat. Laptops get really hot and heat is one of the biggest enemies of electronics. So, with regard to a laptop, you probably want to shut it down at night so that the laptop isn't generating heat all night long needlessly. In addition, your LCD screen has a limited lifespan, just like your hard drive. So you may want to minimize it’s on-time.

The advantages of leaving your computer on all the time are....convenience, your Mac is always ready to go. Less wear and tear on switches and the like during startup (there is some electrical surge when starting up, and computers usually fail, when and if they fail, during startup). Less heat cycling (which tends to cause cold solder joints to form.)

I leave my computer on if I will be coming back to it within an hour or so. Otherwise I shut it down. But that’s not right or wrong, it’s just what I’ve chosen to do.


Randy B. Singer
Co-author of The Macintosh Bible (4th, 5th, and 6th editions)

Macintosh OS X Routine Maintenance
OS X Maintenance And Troubleshooting
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