I'm virtually as much of a novice as you are when it comes to overclocking and certainly wouldn't presume to question the experts here on what's best or how to achieve things, but I will show you what I have done tonight. I also have a PhenomII x4 955, the full rundown for comparison with yours is
Mainboard: GA-MA790FXT-UD5P
CPU: AMD Phenom II x4 955
Memory: Corsair CM3X2G1600C9DHX (4x2GB) DDR3
Hard drives - 2 x PATA (60GB & 80GB), 3 x SATA (1 x 80GB, 2 x 160GB) and 1 SATA SSD (OCZ Core series 32GB)
PSU: Corsair TX850W
Case: 19" rackmount turned sideways to make a deep but low tower
As you can see, I've got a relatively small power supply compared to yours, but even then I think its a bit over specced for my system. Currently I'm pulling about 470 watts total from my UPS, and that includes the power for the monitor (17" CRT), speakers, printer (idle inkjet) plus a couple of other low power accessories. So, by my estimate I'm using perhaps 250W for the PC itself. My drive arrangement also ins't designed for outright speed, the 60GB PATA drive being my primary drive (forced on me by a quirk of Windows) where I have the 32bit XP I'm currently using installed. I also ahve 64bit Windows 7 (installed on one of the 160GB SATAs with the boot code on the 60GB PATA drive), and I'll shortly be installing 64bit OpenSuSE 11.1 on the 80GB PATA, with the rest of the drives being used for storage and applications. The SSD I'm using as a bit of a speed booster. Its too small to sensibly install any operating system directly onto it and give it room to work, so I've split it in three. That's 2GB of swapfile for OpenSuse, 10GB for Windows XP and 16GB for Windows 7 (the 'missing' 4gb aren't missing - 32GB based on 1000 of bytes ber KB and so on equals 28GB based on 1024 bytes per KB etc). I've used these partitions for windows to hold the temporary files and page files on the basis these are the most frequently accessed files and therefore this should give the best performance for what I have.
Anyway, back to the matter in hand. Just before I started writing this I've did a little tweaking and whilst I've been writing I had the CPU multiplier set to 20 giving a core CPU speed of 4GHz which can be confirmed from the attached screen shot. You will note everything else is standard. The FSB is untouched and the core voltage normal. The only other item that could be considered overclocked is the memory (1600MHz), but that is only because the memory is rated for that speed and I have set the machine up accordingly whilst the chipset officially runs to 1333MHz. What I have also just nocited is I forgot to increase the memory voltage to the 1.8V Corsair specify which means its acutally running slightly under voltage, although it seems happy enough doing this. So far the PC must have been running like this for aboutthree quarters of an hour. What has surprised me the most is the power and CPU temperature have both remained at the same level as they do at the stock 3.2GHz speed (16x multiplier) where I had expected them to increase dramatically.
Now, this is where I bow to the experts in deciding whether this is a valid overclocking result as, during that time the PC has only had to cope with me typing this reply and the few monitoring utilities I had running to keep an eye on things so its hardly been working hard. All I've proved so far is this CPU is stable at 4GHz when not having to work hard. Also, I do not know if this overclock would give truly beneficial results as it applies only to the CPU core clock and therefore would only show full benefits on threads that remain inside the CPU without needing to use data from outside. I would be extremely interested to get the opinions of the veteran overclockers on my results as they seem far too easy to achieve and, I suspect if I were to load up the machine properly whilst running at this speed I might begin to see problems, but it does at least show the potential this AMD CPU has for overclocking.
