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Leave it On? Turn it Off? WHY?!

Cheryl from Caldwell Oh. writes:

I have heard that you should shut your monitor off but leave the CPU on, what is the reasoning for this?

Hi, Cheryl.  This is actually a question that has plagued geeks practically since the beginning of computers – and if you ask three geeks, odds are that you’ll get three different answers. Since you asked this geek, here’s my answer…

The idea of turning monitors off when not in use goes back to the days of monochrome CRT’s, PSS (Pre Screen Saver).  These things suffered a malady that has returned to plague plasma TV owners called “burn-in”.  That’s when an image is left on a screen for a long period of time, it literally “burns” into the screen.  Here’s a pic of an old Pac-man video arcade screen that has burned in.

Bear in mind, as you look at this, that the screen is not only off, but also removed from the video game.  The situation is less serious on Plasma TVs, because a plasma screen will eventually “heal” a burn-in when it has had enough varying images displayed on it, whereas old CRT’s wouldn’t.

So back in the old days, when you had a mainframe or something that you had to leave on all the time, the common wisdom was to turn off the CRT’s when not in use to prevent burn-in.  Screen savers eliminated a lot of these problems because they could be set to display a shifting image of some sort.  With the advent of LCD’s, burn-in became largely a thing of the past for computers.

Now the main reason to turn your monitor off when not in use is to extend its life.  Modern LCD life spans are calculated in display hours.  The thing to bear in mind, though, is that the life expectancy of most modern LCD’s is somewhere around 100,000 hours.  How long is that?  Let’s put it this way… if you left your LCD on twenty four hours per day for ten years you would age it about 85,000 hours.  In other words, it’s not a real worry.

The primary reasons to shut off your CPU (tower) are two-fold.

This first is that you may want to shut it down when you’re not using it to save wear and tear on your machine.  Lots of little moving parts and things carrying electricity and stuff that wear out more quickly the more that they’re used.  There’s also the possibility that a power surge or something may hit that damages your machine if it’s on.

The second is that, every time that you run a program, little bits and pieces of that program are left in your RAM.  Enough of these little bits and pieces will eventually cause your machine to slow down. Because of this, I’d recommend that you reboot your machine at least once per day to clear these out.

The main reason to leave your CPU on is that it’s constantly in a “ready” state,so when you go to use it, it’s all ready to go.

One way to fix all of these problems (except for the bits left in your RAM) is to use your machine’s power options to turn your monitor off and put your machine to sleep after a certain amount of time inactive.  Then, when you’re ready to use your machine, all you have to do it click or move the mouse to wake the machine up.

Hope that this helps.

~Randal Schaffer