How Not To Overclock A Clarkdale
There's good news and bad news tied to our overclocking endeavors, as can often be the case when you push hardware harder than it's supposed to go. First, the good news: we achieved a substantial overclock of 4.5 GHz on our retail Pentium G6950 CPU in preparation for this story. We throttled it back to 4.41 GHz to keep the temperatures in check for our benchmarking runs, yielding an impressive 1.61 GHz over the stock frequency.
Now for the bad news: it doesn't count. We killed the processor. Bolstered by reasonable temperature reading and a bit of overconfidence, I pushed the Pentium too hard. My choice of voltage was likely the murder weapon: I set it to 1.475V. In my defense, these are still very new chips, and this is the first G6950 in our lab. There were no warning signs and the CPU lasted through a couple hours of Prime95 testing. Halfway through the overclocked benchmarking runs, the CPU simply died. Not while stress testing Prime95, mind you, but during the AVG virus scan benchmark. Therefore, there will be a follow-up to this article in the next couple of weeks when our replacement arrives. I will be going a second round with the G6950, and this time I'll be limiting myself to a maximum 1.4 V. I will also be testing the CPU on a budget Intel board in the same price range as the Asus M4A785TD-V EVO we used to test the Phenom II X2 555.
Obviously, the results we achieved at 4.41 GHz are not indicative of a sustainable overclock for the components we had on-hand. I did struggle with whether or not to share them in this article. In the end, I decided to include them for curiosity's sake. I know if I were a reader (and not the writer), I would have liked to at least see them. And despite that fact that they aren't really valid from a real-world standpoint, they do give us a glimpse of what a Clarkdale can do at high clocks. It is quite possible that some G9650 CPUs out there might make hit these frequencies more easily with a lower voltage setting.
How To Overclock A Phenom II Black Edition
Here's a CPU we have many more hours of overclocking experience with. At 1.5V, a setting proven quite tolerable by AMD's 45nm Phenom IIs as long as the temperatures are kept in check, our Phenom II X2 555 sample made it to a stable 4 GHz. It couldn't handle 4.1 GHz, though. Knowing that was close to the CPU's upper-bound, we pulled the multiplier back to 19 so that we could increase the HyperTransport reference clock and get a boost from the faster interconnect and memory speeds.
In the end, we took the Phenom II X2 555 to 4.065 GHz with a 213 MHz reference clock and a 713 MHz (1,426 MHz DDR) memory speed:
This provided a nice 850+ MHz boost over the stock speed, facilitating a sustainable 24/7 overclock. We should also mention that we left options like Cool'n'Quiet and C1E enabled, as we appreciate the flexibility of low power usage when the machine is not being taxed. This is something that most users will decide as well.