Most fans blow on, rather than blow off. The surrounding air is cooler than the immediate air on the heatsink. As for the other Q., usually you want cool air from the frt. side and allow rear fans to exhaust. This causes air circulation/exchange. Further, secondary video fan(s) usually are larger like 90mm or even 120mm, to force air over the card area, just to circulate it even more, so it helps. There are all kinds of fans now and their uses vary or adapted, its up to you as it applies to situation. I suggest visiting some "modder websites" to hints/tips/clues on the topic as they generally deal with such issues to include OC'ing.
good luck -----Willy
I'm about to buy an ATi radeon x700, and intend to overclock it a little. Please look at the following picture of the card before you read on:
Now, would the fan be blowing hot air away from the card, or sucking in cold air? If it does suck in cold air, and I buy a PCI card/fan (used to cool PCI cards), and install it directly below the video card, will it just compete with the fan on the video card (it would be directly below the fan on the video card trying to suck in the same cold air), and make it harder to cool, or would it help to cool the card.
Also, does anyone know of any PCI card/fans, that take in cold outside air, and blow it into the case??