Many ppl have sais that the amd fx-4100 will bottleneck the 7970 gpu as i already did expect but with about how much in fps whould the bottleneck be? and how much better peformance whould i get if i get a amd fx-8350 cpu in fps about?
cpu: amd fx-4100
mobo: asus m5a99x evo
ram: kingston 16gb 1333 mhz 4x4 gb sticks
gpu: asus radeon hd 6850 atm but have ordered a gigabyte 7970 oc 1000 mhz so i should get it next week
storage: 120 gb ssd 60x2 ocz and 1tb normal hdd
cooler: antec kuhler 620
case: fractal design core 3000
psu: thermaltake 730w
It depends how well the game can utilize the cores. Look down at the last three in this benchmark, for instance.
If the games only uses one two cores it might become a bottleneck depending, FX 8350 is no exception, because the cores are not really but more a part of a core - one module which can be seen a "core" is made of two bulldozer cores that have two integer units but share a 256bit FPU. Steamroller will solve the "poor" (everyone has to decide where is poor or not) performance in single threaded application such as iTunes partly but not entirely. Older games usually use up two cores which can cause issues.
The difference betwen them is a few fps but if you compare to an intel cpu the difference will vary much more.
Overclock the cpu and the bottleneck won't be to obvious, around 4GHz or more. When overclocking you want to disable the turbo function, function thermal that makes sure that the cpu says within its TDP
FX 4100 will be good til around the 7870, after that you either want to up it to the 6300 or 8320/50. But as Logainofhades said steamroller is just around the corner so I suggest you get the card and deal with it for a while and just upgrade the cpu when the time comes.