1. A computer system, comprising: a voice-recognition module, receiving an external voice signal via a microphone, and determining whether the external voice signal corresponds to one of multiple operation instructions; a shared memory, configured to store shared state information; a microcontroller, setting the shared state information according to the one of the multiple operation instructions when the external voice signal corresponds to the one of the multiple operation instructions, wherein different shared state information corresponds to different operation instruction of the multiple operation instructions, wherein the microcontroller is independent from the voice-recognition module; a power-management module, generating a power-management signal according to the shared state information in the shared memory; and a central processing unit, performing a processing operation corresponding to the one of the multiple operation instructions according to the shared state information in the shared memory when the power-management module issues the power-management signal, wherein the power-management module further generates an interrupt signal to the central processing unit, and wherein when the central processing unit receives the interrupt signal, the central processing unit performs the processing operation corresponding to the one of the multiple operation instructions according to the shared state information in the shared memory.