The 15-second rule and other (non) myths

Last Updated on October 17, 2017 by Dave Farquhar

Cnet investigated some computer wise tales, myths, conventional wisdom, or whatever else you want to call it. The one I take the most issue with is the 15-second rule. They asked Geek Squad, and, as a long, long-ago Best Buy employee, the answer they gave to the 15-second rule is, well, what I would expect.

The 15-second rule

the 15-second rule
Yes, there’s a very good reason to wait 10-15 seconds between presses of the power button.

I remember it as the 10-second rule, myself. Considering the age of the computers running in my house, I’ve been doing something right.

I guess Geek Squad’s answer about it being easier on hard drives sounds plausible, but the rule also applies to computers that don’t even have hard drives. There are two reasons for it: Clearing memory, and plain old stress.

Think about why you shut down your computer. Often it’s because it’s acting goofy. So you shut down to clear the memory and start over from scratch. Well, the memory doesn’t necessarily always zero immediately. I observed this myself in grade school, when bored kids used to cycle the power on Commodore Plus/4s (remember those?) as quickly as they could. The Plus/4 didn’t initialize its video memory right away, so you got random garbage on the screen when you first powered it up. If you cycled the power quickly, you saw some of the bytes went to random state, while others did not.

Theoretically, now that we’re (almost) all running operating systems with protected memory space, and initializing memory to a known state is a common security practice in modern software, that’s less important now.

So, what about stress? Think about rapidly cycling power on a light bulb. Do that enough times and the filament burns out due to the stress. The electrical traces in a computer chip are far, far smaller than the filament in a light bulb.

So, yeah. Follow the 15-second rule. Best practices change, but the laws of physics do not.

And keyboard cleaning…

Yes indeed, cleaning keyboards (of the wired variety) with water is an old trick. The article is incorrect about using soap and hot water. The only reputable Commodore repair shop in the St. Louis area in the 1980s did exactly that, and it worked every time. The trick is to make sure you rinse it thoroughly, and dry it thoroughly. Heat and soap aren’t necessary, but they can help.

Now, would I bother? It depends on the keyboard. I’ve done it with my IBM Model Ms, as they’re no longer in production, they don’t turn up every day, and they cost $100 and up when they were new. I’m less likely to bother with a $7 keyboard, since everyone’s always trying to give me one of those anyway. Everyone has too many of them.

Is turning off your computer bad for it?

This has always been controversial, and the controversy rages harder now than perhaps it ever has. All I know is what I’ve seen. Computers in the server room fail, but rarely. They’re usually obsolete before the hardware starts failing. And most failures are disk crashes, and when you have hundreds of them, a few are going to go out every year. When I did desktop support, the departments that left their computers on all the time had fewer hardware failures than the departments that shut theirs down. Physics doesn’t change.

The question is what costs more: the electricity to run the computers, or the downtime and replacement hardware. The difference today is that computers are much cheaper than they ever have been, electricity is more expensive, and today’s computers use a lot more of it than yesterday’s computers did. There was a time when a whole computer used 60-100 watts; today it’s not unheard of for a computer to use 10 times that.

If electricity is the problem, then solve it right. Shutting the machines down at night is only part of it. The majority of office work is word processing, spreadsheets, and e-mail. Low-power Atom CPUs are more than capable of that work. A modern answer to IBM’s failed PS/2E computer, featuring something along the lines of an quad-core Intel J-series CPU, and a 128 or 256 GB SSD would knock that usage back down to, or even under, the 60-watt range. Current chipsets will even take 16 GB of RAM. The trouble is, none of the major builders of business-class PCs is marketing anything like that.

Like the 15-second rule, leaving PCs on reduces stress and increases their life expectancy.

Deleting data for good

Deleting data off a hard drive is difficult–that’s part of what got Oliver North in trouble–but it can be done, and you don’t have to resort to using a drill. Use Darik’s Boot and Nuke (

Is Darik’s Boot and Nuke guaranteed to completely obliterate everything? No. Is drilling 12 holes in the drive? Actually, no. The best you can do is make it so difficult and expensive to recover the data that it’s not worth it. I’d rather do it with a piece of software that overwrites the drive with random data multiple times than with a power tool. Just fire it up and walk away. The effort involved is minimal, and the chances of injury are even less so. Here are some other hard drive destruction tips if you need them.

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One thought on “The 15-second rule and other (non) myths

  • December 22, 2010 at 3:57 pm

    We do the “five-second-rule” in my house … maybe I should make the kids do it twice between reboots. The only machine I ever actually damaged by not waiting 10 seconds was our old TRS-80 back in 1982 — and wouldn’t you know it, it was right after my dad put it up for sale.

    As for shutting down machines vs. leaving them on, I did a study once on our old HP servers here years ago and close to 80% of our hard drive failures came during reboots. Those things would run forever, but each time we rebooted them and those hard drives would spin down and back up, we would hold our breath. Like everything else, technology has advanced over the past decade, and I can’t remember the last time I had an internal hard drive just up and die with no warning. In fact, the last two hard drives I had fail were both USB drives without external power adapters. I assume they either died from getting banged around, or from not getting enough power.

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