This paper proposes an ultra fine-grained run-time power gating of on-chip router, in which power supply to each router component (e.g., VC queue, crossbar MUX, and output latch)

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Geyser-1, a prototype MIPS R3000 CPU with fine grain runtime PG for major computational components in the execution stage is available. Function units such as CLU, shifter, multiplier and divider are power-gated and controlled at runtime such that only the function unit to be used is powered-on to minimize the leakage power. The evaluation results on the real chip reveals that the fine grain runtime PG mechanism works without electric problems. It reduces the leakage power 7% at 25 • C and 24% at 80 • C. The evaluation results using benchmark programs show that the power consumption can be reduced from 3% at 25 • C and 30% at 80 • C.

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A highly energy efficient reconfigurable accelerator called CMA (Cool Mega-Array) is proposed. It consists of a large Processing Element (PE) array without memory elements for maintain result of ALU and configuration data, a small simple programmable micro controller for data management, and the data memory. Unlike traditional coarse grained reconfigurable processors, the power consumption for hardware context switching, storing intermediate data in registers, and clock distribution for them are eliminated from PE array which occupies large area of a chip. Configuration registers are collected to small area of micro controller. The data flow graph mapped on the PE array is static during execution. Various application programs can be implemented by making the best use of flexible data management instructions with the micro controller. When the delay time in the PE array is longer than the data handling time with the micro controller, the supply voltage for the PE array is scaled to reduce the power consumption without degrading the performance. In the opposite case, wave pipelining is applied to enhance PE array performance. A prototype chip CMA-1 with 8 × 8 PE array with 24-bit data width was fabricated in 2.1 × 4.2mm 2 65-nm CMOS technology, and achieves 2.4-GOPS/11.2-mW sustained performance. This energy efficiency is comparable to that of the most energy efficient accelerators that have been reported.