how can u tell how hot ur vid card is

and how do u know what is too hot?

Google can tell you whats to hot, or if you start to see little dots uselly white ones on the screen. Thats a sign of overheating. As for monitering it. New cards have probs that tell you the temp but on a old card you have to manuelly install a probe or use a digital temp reader, like a thermominter.

Many newer video cards have temp sensors & thats how you can find out the temp of a video card. The 9800XT, 6600GT, 6800 series, & the x800/x850 have temp sensors (correct me if I'm wrong about the last two) have them. I'm sure there are others with them too. The manufacturers have published limits for the cards. Thats how you know whats too hot. IIRC its around 100°C for most video cards. Its a good idea to keep your GPU as cool as possible of course.

EDIT: Yeah I forgot to add, artifacting can be caused by too much heat or too high of an overclock combined with heat or too little core voltage for the video chip.

do u get a fps boost

do u get a frame rate boost from o/c a vid card?