It is stated above that the MFC “….runs at speeds of 2.5, 5, 10 and 20 MegaHertz”. Why the different speeds instead of just running it at the maximum speed?
The MFC runs at different speeds to save power. There is a direct correlation between the speed of the processor and the amount of power consumed and the processing capability. At 20 MegaHertz, the processor can process about 22 Million Instructions Per Second (MIPS) while at 10 MegaHertz it can process only about 11 MIPS. At 20 MegaHertz, the processor uses about 9 watts of power. Dropping the speed in half to 10 MegaHertz will reduce its utilization to about 5.5 watts and at 2.5 MegaHertz it will use about 2.5 watts. This capability to run at different speeds allows us to tailor the speed and power utilization of the MFC to match the tasks we are processing and minimize the power used. Power is a critical resource for any space mission and any reductions in power utilization can aid in making the spacecraft lighter (by using smaller batteries and solar arrays) or capable of allocating power to be used to do more scientific work or take more pictures, or conduct a longer mission, etc.
