AMD Phenom II X4 940 & 920 Processors

Overclocking:

Since this chip is a Black Edition (unlocked multiplier), I simply used the AMD Overdrive tool to increase the multiplier and adjust the CPU voltage. I spent a lot of time trying every voltage possible and trying every trick suggested to me when a barrier was reached. Some of the Phenom II processors like a lot of voltage, mine tended to be most stable around 1.45V - 1.575V when overclocking.

For every 100 MHz bump in speed it seemed like there was always a need to bump up the voltage just a little too. They can be real finicky, I suggest always writing down your speeds & voltages so you know what you've tried and what you haven't.

For air cooling I tried a Zalman CNPS-9700, a Scythe Infinity, and a Cooler Master V8. All performed excellent, but I have to say the best was the V8. For loading I ran Prime95 for a while till the CPU temp stabilized. I went up to about 1.6V on air but never could get stable any higher than 3.7 GHz.

For phase change I used my trusty old Vapochill XE II (amazingly the software will run on Vista x64). There were ZERO problems running sub-zero temps, the colder you can get this chip the better it seems to run. As you can see in the BIOS picture, the CPU temp would get down to about -21°C on my Vapo. The only program I found that would read the negative CPU temp properly (besides looking in the BIOS) was good old SpeedFan.

4.1 GHz was almost stable on phase. I could bench long runs okay, but stability testing programs would fail after a while. 4.2 GHz I could bench SHORT runs, i.e. wPrime 32M. Finally, 4.3 GHz was pretty much only good for a screen-shot... 4.4 GHz would cause an instant crash. I tried up to 1.7V on phase, I was just waiting for my CPU to pop at that voltage, but it still is running like a champ. For my CPU, anything beyond 1.575V or so would have start to have negative effects on stability... go figure.

Here's a breakdown of the numbers:

• 3.0 GHz / 1.35V / 43°C = Stock
• 3.5 GHz / 1.35V / 44°C = Max Stable Air OC @ Default Voltage
• 3.7 GHz / 1.4625V / 50°C = Max Stable Air OC
• 4.0 GHz / 1.525V / 9°C = Max Stable Phase OC
  • 4.3 GHz / 1.525V = Max Unstable Phase OC

Overclocking Benchmarks:

Here's a few benchmarks to show the relative performance of the Phenom II X4 940 running at 3.7 GHz (max on air) and 4.0 GHz (max on phase). To compare I clocked a Q9550 up to the same 3.7 GHz as a "clock for clock" comparison.