Ah, well there are things called fan curves which has become a more increasingly common tech that has gone into both AMD, and Nvidia cards which basically means that when your card reaches above a temperature limit your fan speed increases. Also, case fans are helpful with creating more airflow for your system and your graphics card. Different cards have different abilities to approaching how hot a card can get but I would say for the most part that any current gen card will due a sufficient job cooling the chip.