AthlonXP Underclocking for a Low-Power Fix

Lower Speeds Just By Halving The FSB Clock

Less than 100 MHz FSB clock (FSB400) is not possible on Intel's Socket 478 systems.

Halving the clock speed did the trick: At just 100 MHz FSB clock the Pentium 4 2.8 GHz in idle mode showed power needs of approx. 8.4 watts. Unfortunately, the power loss under load is still phenomenally high - our measurements with Prime95 showed 31.2 watts at 100% CPU load.

We pitted the 3.0 GHz sample of the P4 Northwood into the running with a x14 multiplier at 100 MHz FSB clock speed.

At a CPU speed of 1,400 MHz, the die temperature clearly cooled to as low as 34.5°C in an open system using the boxed cooler from Intel.

With the help of the ClockGen tool, the FSB can be switched down to 100 MHz during operation.