I found this thread on here a while back and its for a phenom II 940 (which i have) but all the phenom II x4's are close. I hope this helps and here is the link
http://forums.amd.com/forum/me...d=107153&enterthread=y
That last link helped me choose the right voltage to be stable and i am currently running at 3.5 Ghz from 3.0
http://www.techreaction.net/forums/showthread.php?t=367
This link is a guide for the phenom II that is good so check it out.
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Motherboard: ASUS M4A79 Deluxe
CPU: AMD Phenom II 940
Ram: 6 GB ddr2 pc 6400 800mhz
GPU: 2 ATI Radeon 4890
1.2 GB HD space RAID 0
Rosewill Xtreme Series RX850-S-B 850W
Cooler Master Hyper 212+ cpu cooler
Cooler Master HAF 932 AMD edition
Windows 7 64-bit