| 摘要 |
A CPU (10) has a powerdown mode in which most of the circuitry does not receive power. Power-up (64), coming out of powerdown (58), is achieved in response to receiving an exception (60). Because most of the state information that is present in the CPU (10) is not needed in response to an exception (60), there is no problem in removing power to most of the CPU (10) during powerdown (58). The programmer s model register file (16) and a few other circuits in the CPU (10) are maintained in powerdown (58), but the vast majority of the circuits that make up the CPU (10): the execution unit (20), the instruction decode and control logic (18), instruction pipeline (26) and bus interface (32), do not need to receive power. Removing power from these non-critical circuits results in significant power savings during powerdown. The powered circuits are provided with a reduced power supply voltage to provide additional power savings. |
