I was just surfing online and suddenly my monitor screen dropped to half-sized, black on the top half, with a white bar of light about 1/4" wide across the middle, and the web page below.

This is NOT shrinking down to a small box in the middle of the screen, it was half of the entire screen.

It lasted for about 15-20 seconds, then went back to normal.

Any ideas?

Sue

What type of monitor (CRT or LCD)? Did you have a power drop (a "brownout")? Power issues could cause something like this on a CRT monitor, but probably not on al LCD one. Was you computer excessively busy at the time, possibly overheating the video card?

WARNING: Due to recent budget cuts, we have had to reduce your web surfing experience by half. We're sorry for any inconvenience. -The Management

Is it linux? I've had similar situations w/driver failures...but it warns you after it happens, so probably not the case here.

It sounds like the computer briefly dropped into a video mode that the monitor can't do.

This can happen when the video cable is loose or broken inside causing the computer to misread the EDID data (EDID is the information the monitor sends to the computer listing the monitor mode capabilities).

But if the EDID data is read wrong then I'd expect lots of other brief glitches on the screen from video signals too.

Failure modes that come to mind:

-Power line voltage drop.
-Power line voltage surge triggering surge arrestor or over-voltage limit in power supply.
-Loose connector: at wall socket, power cord to PC, adapter to monitor, power supply to graphics adapter.
-Graphics adapter not seated properly in slot.
-Failing/overheated graphics adapter, PC or monitor power supply. Dust buildup or failed fan most likely cause of overheating.


Most of these can be ruled in/out in a couple of seconds. When was the last time the PC got a good cleaning? I've seen a lot of unreliable computers that just needed the dust cleared. It is a really simple job.

Susan. Your CRT monitor is at the end of its life span.

LCD monitors can do this too - I have one system that does something like this most times it boots until the OS is loaded and the video driver started.

The option ROM on that video card isn't good enough at rejecting bad EDID reads and defaults to a video mode half the resolution that monitor can support. When the OS & its video driver take control they switch to the last video mode I used, which works.

Normally fried electronics can't sync at all, but that's not what happened to Susan with the web page stable on half the screen - it stayed in sync, with a wildly bad sync rate.

You're supposed to clean them?

How much dog hair, cat hair, dust and woodstove ash can they hold?

It's nothing fancy, just a cheap home computer. Linux probably isn't an issue, whatever it is.

Sue

This can happen when the special energy waves "they" are beaming at your head interfere with your monitor.

I suggest tin foil around your monitor and your head. Don't be fooled by those who claim you can use aluminum foil to protect yourself and your monitor though. Only genuine tin foil is effective.