the criteria established by the designer or programmer for identifying significant do loops as previously explained suitable do loops can be detected by monitoring the instructions being generated by master controller 40 for the presence of pre determined sets of instruction sequences indicating that a significant do loop is beginning persons of skill in the art will understand how to do this based upon the teachings herein and well known general computer programming principles fig6 is a flow chart illustrating a preferred embodiment of conserve power method 80 of the present invention method 80 begins at query 82 wherein a do loop start is detected by master controller 40 or repetitive instruction controller 50 if a do loop is not detected outcome 34 no 34 then it loops back via 83 to the input of query 82 if a do loop is detected outcome 34 yes 34 then method 90 proceeds to step 84 wherein the system is initialized as previously described controller 50 generates loop flag lf signal 64 and first loop flag flf 66 subsystem halt controller 52 receives these and generates subsystem flag ssf 68 for example aflag bflag nflag addressed to the various subsystems in query step 86 the subsystems.