The changes:As far as I know all Intel Prescott processors made on the 90nm process with 1MB L2 cache will feature this update. Sampling of processors with this update will start on the 27th of February according to Intel.
CPUID will change from 0F33h to 0F34h D-0 will feature power optimizations to enable speed enhancements. Most likely these chips will also become less hot? For the rest the D-0 is fully the same as the current Prescott with C-0 stepping.
Qualification is planned to end on the 23th of April, and first retail Prescott CPUs with this update should be arriving around the 7th of May.