It looks like a switching regulator for a cpu. It powers the cpu from tick over mode to full power in a fraction of time a psu can do. It is usuall used for P4 processors with hyper threading technology. When the cpu is in tick over mode it uses little current, so it keeps cool. When the DMA and hard cache needs procseing power teh unit fires power to the cpu.
Feed in is from the psu and feed out to the cpu.