Saving Power through Explicit MechanismsThe Power/Performance DilemmaOur SolutionAreas that can be optimizedThings to worry about…Execution PlanSaving Power through Explicit MechanismsDave Maze, Edwin Olson6.893, Fall 2000The Power/Performance Dilemma•Mainstream architectures focusing on high performance•Some applications require low power•Usage patterns of some devices call for short periods of high performance and long periods of low-power performance.Our Solution•Build a machine which can yield adequate performance, but can switch to a low power mode.•Turn functional units and capabilities on or off depending on performance/power needs.•Have the compiler make as many decisions as possible (minimize hardware profiling required)•Explicit instructions for coarse granularity, extra bits in instructions for fine granularity.Areas that can be optimized•Turn off sections of cache to reflect size of “working set”•Put functional units into a “coma” mode•Turn on/off out-of-order/speculative issue logic (resulting in an in-order microprocessor)Things to worry about…•Existing work exists. Try not to duplicate. Try to do something novel.•Code density – perhaps we’ll ignore code density for this phase of research.•Compiler hacking – perhaps we can sidestep the issue by doing some assembly hacking to get approximate results.Execution Plan•Begin by testing ideas/profiling benchmarks to determine effectiveness of particular ideas.•Select an idea, hack together an approach, and measure results. (Checkpoint 1, Oct. 19)•Refine, extend, automate optimization (Checkpoint 2, Nov. 9)•Tools: SyCHOSis, MIPS ISA
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