unclefester is right. Not only that but I have a 790FX-GD70 as well, it took me a while to find my 955's sweet spot, 3.9 at 1.49v. Because not all CPU's are manufactered perfectly, you sometimes have to look at the "quality" of the stepping. Some people with the 955 can easily hit 4.0ghz while some like me not so lucky. IT's a trial and error so no quick way for you.