If you overclock your GFX card too much, what damage does it do?

I know that overclocking CPU's too much burns them out (as it usually requires voltage increases), but what happens to graphics cards when you overclock them too much (as you can't, easily, increase voltage)?

What affects would you see on your screen, or in your boards benchmarking or testing?

Any articles on this already?

I've never burnt down a video card before but i've seen a picture of one... i started getting artifacts on the screen after i pushed my gpu and memory too much 260/540... i think if you leave it like that for too long it will be damaged permanently... i went a little lower and some of the letters on my screen still looked funny... i think my max is 250/535 but i still have the stock heatsinks on my ram so i left it at 250/500...

Well on some older cards that I overclocked I got strange artifacts on the screen even in regular 2d mode. These were some voodoo 3000 cards and I really don't overclock my vidcard since.

Well besides heat damage, I've heard of memory thats gone bad, causing permanent graphical artifacts, even at stock speed. With proper cooling and without overdoing it you'll probably be fine.

You'll see graphical artifacts on the screen (white specs, textures missing, bad clipping) when you've pushed too far. Or it will just lock things up.

-Rav

I destroyed a voodoo 3 3000 by overclocking it too far. with a blue orb on the GPU and stock heatsink on the back. Now it still runs, but only for a few seconds, when I pull it out of the case the ram is so hot that you can’t touch it, and the blue orb is close to melting point.

Lol this is getting to be a video card overclocking horror stories thread.