BSEL and Vcore boost mods. These would be hardware mods.
BSEL is a set of contacts on the bottom of the processor.
It allows the processor, to tell the clock generator, what
speed to use. Your processor is FSB1066 (266MHz). By
changing the BSEL signals (fooling the clock generator),
you could jump to FSB1333 (333MHz). Your core speed becomes
(1333/1066) * 2.66GHz = 3.33GHz core speed.