overclocking my gfx card

[SpRi7e]

I'm just wondering, I'm going to overclock my graphic card for the first time and i'm going to use rivatuner 2.0 to do it, and I'm just wondering if graphic cards have a certain limit that it can be overclocked to or it won't work and if I buy a good cooling fan that it would be able to go higher. I have a xfx 7800gtx and it's usually idle at 41 c

 

[kobe24]

use ati tool and scan for artifacts for aleast 10 mins if it doesnt come up with any go higher

 

[SpRi7e]

Well I just overclocked it until the artifacts started coming up and stopped it and I'm wondering if I get cooling then would I be able to get it higher without artifacts or is it just at a preset limit?