Why are the edges of my screen moving?

[bwkaz]

I don't see the problem, usually, but recently it's gotten worse -- when I drag a window around on the screen (in either Win98SE or Linux -- Mandrake 7.2, KDE), the edges of the screen move with it. It's like wherever the window currently is, the scanlines go a little farther to the left and right, and it gets really noticeable when the window moves. It looks like the window is "pushing" the screen out a little. I recently went from 1152x864 res to 1280x1024, so that could have something to do with it. I've been running the system at 16bpp the whole time. I have a 17" Dell M781s monitor, and the whole system is running at I think 75Hz refresh (it's set to Optimal, but nothing looks different if I set it to 75). I've got a 3dfx Voodoo3 3000 video card, and the newest (and last, it looks like -- ) drivers from 3dfx.

Anybody know how I could fix it? I could live with it if needs be, but it's a minor annoyance that I'd like to get rid of if possible.

Thanks in advance,

Bryan

[This message has been edited by bwkaz (edited 02-05-2001).]

[justy]

I assume what your moving is brighter than the backround?

It's not a fantastic monitor, and at them rates, I'm not suprised to see some movement. Do you need it at such a high resolution? I know this is not what you want to hear, but I have very few good experiences with Dell monitors.
If you drop the resolution does it cure the problem?
Does the screen shake, always? or only when you put a brighter object into a corner?

If it shakes all the time, then you've got a fault. Post back with more info.

All the best, Justy.

[justy]

Sorry double post.

But I actually reread the above and it sounds a bit cruel. Not intentional.

If it is a fault I would be glad to help in any way I can.

All the best, Justy.

[This message has been edited by justy (edited 02-05-2001).]

[bwkaz]

It doesn't really shake at all. It's just that the left (or right) edge moves a little when the window gets close and moves up & down. Yes, the window is brighter than the background -- a basically pure white window vs. a half-intensity cyan (i.e. RGB value of 0,128,128) desktop. It doesn't do it with white-on-white. And it does happen at every lower resolution I tried, down to and including 800x600. I just never noticed it before, I guess. It does it at 60Hz, too, and I can't change the refresh to anything other than 60 or 75. You're very right, it's definitely not a fantastic monitor. I have no delusions of the monitor quality, I was just wondering if it was fixable.

Sounds like it's unavoidable without a new monitor, then? It's fine if it is, I was just wondering. Oh well.....

Thanks,

Bryan

[Peter M]

This effect is known as "pumping".

Poor voltage regulation in the horizontal deflection unit leads to that effect - scanlines with high brightness then become wider than darker ones. Some very cheaply built monitors even "manage" to get variations in display height, depending on overall brightness in the image.

All in all, a monitor that shows a noticeable amount of it is poorly built. That doesn't necessarily mean that it's been cheap though. There are cheap monitors that don't, and you'll always find an expensive one that does, although this is getting really rare.

Regards, Peter