Geyser-1: A MIPS R3000 CPU core with fine-grained run-time power gating

Geyser-1 is a MIPS CPU which provides a fine-grained run-time power gating (PG) controlled by instructions. Unlike traditional PGs, it uses special standard cells in which the virtual ground (VGND) is separated from the real ground, and a certain number of the sleep transistors are inserted for quick power shut-down and wake-up. In Geyser-1, the fine-grained run-time PG is applied to computational modules in the execution stage. The power shut-down and wakeup are controlled with architectural and software level. This implementation is the first available CPU with this type of run-time PG technique. Geyser-1 has both time and spatial fine-grained PG and works well with a real chip.