Dynamic overclocking is a technology which changes CPU clock speed according to load, such as Intel Turbo Boost.
The problem with dynamic overclocking is it distorts Robocode engine CPU constant estimation, leading to inaccurate skipped turns calculations.
How do I disable it?
In Windows 7, go to Control Panel > Hardware and Sound > Power Options and choose High Performance. This will lock CPU speed at 100%. You can instead customize your own power plan, going to Change plan settings > Change advanced power settings > Processor Power management and setting Minimum processor state and Maximum processor state both to the same value.
You may also want to erase config/robocode.properties so CPU constant is recalculated using fixed CPU speed.