To measure the CPU's temperature, we used SpeedFan v4.24. After letting the processor cool down in idle mode, we fired up Prime95 and ran the in-place large FFT test to heat it up to its maximum level. This is the graph of the temperature with the original AMD Socket A cooler:

Starting from 58C...

and the reported fan speed...

The temperature during idle is approximately 58 °C. When we began the torture, test this increased to 65 °C. At the same time, the rotation speed of the fan was between 2720~2820rpm.

We then repeated the same test with the CopperLite cooler installed:

Starting from 34C in idle mode...

the RPM graph under the Freezer 64

The temperature began from 52°C instead of 58 °C and reached 60°C instead of 65 °C. 5 °C difference is not bad at all. The rotation speed of the fan was at 2680~2760rpm. The noise level was rather low but we couldn't estimate the absolute value.

Lower temperatures with lower rotation speeds than the stock cooler, do we need anything more?