If you decide to start an overclocking session with the Phenom processor; typically you are better off with the BE editions (CPU multiplier unlocked), and the combo of an AMD 790 FX/GX based mainboard. In today's test we will use the Phenom II X4 940 BE.

The key to the 790FX/GX feature set is AMD's Windows compatible Overdrive interface that allows graceful overclocking of the Phenom II (and last gen Phenom X4 Black Edition) processors. It's one of the best tweak utilities out there and thanks to AMD's recently introduced Advanced Clock Calibration technology the results on a 790 chipset based platform, will certainly be good.

The new Phenom II processors can complement the 790GX chipset's overclocking capabilities very well. Example: A Phenom II at 3.0 GHz can be pushed towards 3.6 GHz pretty easily on just an air cooler. With real good air-cooling or water-cooling you should be able to reach 3.8-4.0 GHz. And as many news-posts have shown, on demonstrations some freaks were able to super-cool the processor with LN2 and clocked it close towards a geeky 6.0 GHz. If you decide to overclock, then you should be using an AMD 790 chipset based motherboard as this chipset supports Advanced Clock Calibration, okay? ACC, short for Advanced Clock Calibration, really enhances the overclocking potential of Phenom / Phenom II processors.

AMD never disclosed how exactly ACC works, yet one fact is that the Southbridge has a dedicated link to the CPU. We think it boils down to ACC's ability to keep clock frequencies in sync and stabilize inter-chip communications between the CPU, Northbridge, Southbridge and memory. Mind you that this trick only works for Phenom II processors, particularly for the Black Edition processors.

Our overclocking results:

We gave it a try and were able to reach much higher clock frequencies perfectly stable on the fly. AMD's Overdrive software overclocking the Phenom II X4 940 allowed us to push the clock frequency towards 3500-3600 MHz fairly easily, with a horrible low-end air cooler.

My goal however was 3800 MHz, Once I installed a 35 USD OCZ Vendetta 2 heatpipe cooler, the results instantly became more stable. Through AMD overdrive I crammed in 1.5 Volts into the CPU, changed the processor multiplier ... hit apply. And we had a stable overclock.

In this review we'll consistently show you results from our benchmark session with a tweaked processor towards 3800 MHz. Let's have a look at that software.

Overdrive features :

A couple of screenshots of the brilliant AMD Overdrive utility. This is the performance control screen where you can see all primary variables and adjust them. Everything can be adjusted on the fly.

This is the startup screen showing the basic variables. Also a good screen to check out the processor and see if the specs match.