Leave it on? Turn if off? Depends on how you compute it

Personal computers

May 11, 1992|By Michael J. Himowitz | Michael J. Himowitz,Staff Writer

Jeff and Alice just bought a computer for their business. Jeff called last week and asked me to settle a dispute that he said was threatening their partnership, if not their marriage.

"Alice says we should leave the computer running when we're not around because the wear and tear of turning it off and on is worse than leaving it going.

"I say that if we're not using it, there's no reason to keep it on. We keep all our business stuff on that machine. If something goes wrong, we're out of luck. I figure, if it's not turned on, nothing can happen to it."

As you can see, Jeff is a worrier. But the question is a good one, and a common one, judging by the number of times I hear it. The answer, unfortunately, isn't always simple.

From a reliability and maintenance standpoint, there are three significant parts to your computer: the electronic circuit boards and chips inside, your hard disk drive, and your monitor.

The best thing you can do with most electronic components is turn them on and keep them on, as long as they're operating in their normal temperature range -- which is much the same as your normal temperature range.

Cycling the power frequently is not good for delicate circuits and chips. They don't like surges of electricity. Every time you turn them on, they heat up, and when you turn them off, they cool down.

Over time, this can have a particularly insidious effect on chips, which start to come loose in their sockets. You don't know what's happening until something doesn't work. Fortunately, this problem can often be solved by re-seating the offending chip in its socket. Unfortunately, not many people know how to do that.

So score one for leaving the computer on.

Now the hard disk drive. This is the primary moving part of your computer, and the one subject to the greatest wear and tear from constant running.

The important thing here is something called MTBF -- mean time between failures. This is technobabble for how long, on the average, a drive will run before it eats your payroll records or doctoral thesis.

Early hard disk drives had MTBF ratings of 5,000 to 10,000 hours or less. Since there are 8,760 hours in a year, you could virtually count on a failure somewhere along the line. So made some sense to turn the computer off if you knew you weren't going to use it for several hours.

Today, however, hard drives have MTBF ratings of 20,000 to 40,000 hours. It doesn't make much sense to turn them off unless you're going to be away for quite a while.

Your monitor is a different story. If you leave a monitor on for days or weeks displaying the same image, that image can burn itself into your screen. This can be annoying, or it can make your monitor virtually unusable, and you'll have to replace the picture tube or buy a new unit.

You can handle this problem in two ways. One is to turn your monitor off, even if you have to leave the computer running to handle scheduled events. Or, you can invest in inexpensive screen-blanking software. These memory-resident programs turn off the picture or display a constantly changing image if no one has tapped the keyboard for a set period of time.

The important thing to remember is that hardware is cheap and getting cheaper all the time. Your time and data are expensive, and getting more expensive all the time.

All equipment will fail sooner or later -- regardless of whether you leave the computer running 24 hours a day or turn it off every time you leave the room. When your computer does fail, it will be at the worst possible time.

The best way to protect yourself is by backing up your data. Tape backup drives are available for as little as $250. They're easy to use -- you can even back up your data at night, if you're willing to leave the computer running.

If you have tens of thousands of dollars worth of accounts receivable information on your hard drive, or six months of work on the Great American Novel, it's stupid to lose it because hardware breaks down.

So how do I answer Fred's question?

On the whole, I lean toward leaving the computer on if there's a decent chance I'll need it.

If I'm using the computer during the day, I leave it running, even if I'm going to be gone for several hours. At night, I generally turn it off, unless I'm running a tape backup.

During the summer, when thunderstorms are frequent, I turn the computer off and unplug it if I'm going to be away for a while. While I have two or three surge suppressors, none of them will handle a lightning bolt that strikes the power lines out

side the house.

If you're in a commercial building that's subject to frequent power surges (particularly if the electricians like to work at night), it's also a good idea to turn the machine off during extended periods of inactivity. But this has more to do with external forces than concern about wearing out the computer.

Likewise, if your area is subject to brownouts and blackouts -- with resulting power surges when the juice comes back on -- you may be less likely to damage the computer with the power switch than by subjecting it to the vagaries of the local electric company.

Finally, be aware that the leave-it-on theory does not apply to the lights around the house. My wife is a compulsive light extinguisher. I like to leave them on. I argue for the efficiency of leaving the lights on because the wear and tear on the bulb is more expensive than the electricity you consume leaving it on. She calls me a spendthrift and turns the light off.

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