A machine code builder providing improved software controlled power management is described. A machine code builder reads pre-executable code and builds machine code from the pre-executable code to maximize a duration that a resource is not required. The resource(s) not required may be user defined or the builder can analyze the pre-executable code to determine which resource(s) are not required. The builder re-organizes machine code to maximize the time a particular resource is not used. Mechanisms are also provided to have resource emulation code execute during re-energizing of a resource to prevent loss of performance.