Overclocking

We dropped the Athlon II X4 620 into our favourite MSI 790FX-GD70 motherboard and proceeded to crank the HyperTransport bus like it was dispensing £50 notes. With the Athlon IIs completely lacking unlocked Black Edition parts, there's no multiplier adjustment option, only traditional HyperTransport scaling. This means that we need to be aware of other clock factors directly linked to this clock generator: namely the CPU memory controller and (more obviously) the HyperTransport bus too.

As we don't need any more HyperTransport performance we kept this as close to the stock 2GHz clock as possible by lowering the multiplier while scaling the CPU clock. At first the memory controller was also kept as close to a stock 2GHz as possible, until a maximum overclocked CPU frequency was determined, then that was gradually increased too.

We eventually found a CPU frequency of 3,536MHz, with a 2,449MHz northbridge and 2,176MHz HyperTransport frequency was the highest achievable stable clock speed. This included a DDR3 memory frequency of just 1,450MHz as the next multiplier up was too far for the AMD CPU; this did enable us to optimise the timings to 8-8-8-20-30-1T though. The CPU was set to 13 x 272MHz HT at 1.448V, with 1.325V CPU-NB.

We found that the high starting voltage of 1.4V helped it reach around 3GHz without further adjustment, but to change the CPU-NB at all and really push the CPU frequency, more voltage was most certainly required.

While at nearly a gigahertz overclock, we aren't complaining too much, but it seems a little short of what the Phenom II Deneb core is capable of. Perhaps if a Black Edition version ever appears we'll see a bit more clock speed since we won't need to push the HyperTransport bus.

Power Consumption

As we expect, the Propus core, with half the transistor capacity, does respectively well when idling with Cool'n'Quiet enabled. This clocks the CPU down to a 4x multiplier (at 800MHz) with just a 1.15V core voltage. It fits in neatly a few watt lower than the Deneb triple and dual cores Phenom IIs, but as expected uses more power than the Intel dual core - although only by 3W! Two extra cores, three watt difference: sounds great.

The same can't be said for load performance, and that high 1.4V at its full clock speed certainly makes a dent on the power savings as the Athlon II X4 guzzles down some 20W more than the Phenom IIs, not to mention 50W than the Intel dual core. Moreover, for around 30 per cent more transistors the Athlon II X4 requires 35 per cent more power.