Methods, apparatuses, and systems that allow a microprocessor to optimally select an assist unit (co-processor) to reduce completion times for completing processing requests to execute functions. The methods, apparatuses, and systems include assist unit hardware, assist unit management software, or a combination of the two to optimally select the assist unit for completing a specific processing request. In optimally selecting an assist unit, the methods, apparatuses, and systems calculate estimated times for completing the processing request with conventional means and with assist units. The times are then compared to determine the fastest time for completing a specific processing request.