Karaya, *some * of the newer stepping amd chips are *supposed* to have a revision that has fixed the issue of running the reduced speed of 333mhz . Ive looked around for some possible workarounds incase it still happens to you , a few have been able to manual set the memory speed to ddr400 and be fine, some boards auto default to 333 when 4 sticks are present , but are actually able to run at 400mhz. Now *IF* you get stuck @333mhz I would say the difference between 400mhz and 333 is around 7-10% or actuall FPS. I really cant find a relevant benchmark comparision to give you concrete figures.
But regardless, with 4 sticks your still going to be stuck with a 2T command rate . Here is a comparison between 1t and 2T . i would say its about 3-5%
http://www.anandtech.com/memory/showdoc.aspx?i=2560&p=23 STICKS
I dont think that people are having issues running 3 stick at 400mhz, but then your opening a can of worms with Dual channel . Some people say they can run dual channel with a 1gb stick in the first channel , and then the 2X512 sticks in the second channel. But then others say it wont do dual, and that they dont know what their talking about lol . I really cant find anything concrete. Just incase you cant run dual channel with 3 sticks Here is what the difference between single and dual channel equates to. Make sure you look threw the whole article thou ,HL2 uses the CPU more than the GPU, so it really shows a big difference . In GPU intensive games the margin is much smaller . i would say avg 5-7%
http://www.tcmagazine.info/articles.php?action=show&id=128&perpage=1&pagenum=11 Well i hope this doesnt just look like a ramble about nothing lol. Im just trying to lay out the different options , and what the performance impact might be . Alot of this is pure speculation that you are going to have problems. You might be fine . The only thing i know for sure is the 2T command rate . If it were me , I would play it safe and go for 2X1gb sticks . Good luck with whatever you decide .
38