what exactly does FSAA do for a video card and how can it degrade performance?

[Buliwyf]

curious as I am not sure the main differences between 2x and 4x and none......

 

[BFG10K]

FSAA removes jagged edges, edge crawling and texture shimmering by using a variety of techniques which all involve colour sampling to various degrees. It slows down the card because generating the extra pixels, sampling them and then blending them into the final output creates more demands on the memory bandwidth and fillrate of the GPU.

 

[AnAndAustin]

PICS OF AA & AF (Rad9700, Rad8500, GF4TI4600):

Tech Report look at AA

HardOCP look at both AA & AF

In terms of perf hits the Rad8500/9000 work very well with AF, they take only a small perf hit. GF3/4TI work very well with AA although 4xAA does hitt hem too hard, AF is high quality but takes double the hit of a Rad8500/9000. Rad9700 can run with both AA & AF and only take a small perf hit. If you want rough numbers a Rad8500 using 2xAA hits perf by 50% (so it's now at half speed), 4xAA hits perf by 80%. GF4TI using 2xAA or QxAA takes 15% perf hit, 4xAA takes a 50% hit. There's alot of discussion and variation about exactly what AF is, how it should be implimented and what it should look like, the notation also varies and GF4TI's 2xAF is roughly equivilent to Rad8500's 4tap AF, and the same for 4xAF and Rad8500's 8tap. Anyway for rough figures, GF4TI takes 10% perf hit by using 2xAF and 25% in 8xAF, Rad8500 takes only 5% perf hit from 2xAF (4tap) and 10% in 8xAF (16tap). These figures will change depending upon your CPU, precise clock speeds of your gfx card, game engine, detail settings and resolution and these numbers are from old drivers, back when I was looking in to AA & AF for a few people so things should have improved as drivers matured, as I said for a rough idea it's about right.