Manycore chips are emerging as the architecture of choice to provide power efficiency and improve performance, while riding Moore's Law. In these architectures, on-chip interconnects play a pivotal role in ensuring power and performance scalability. As supply voltages begin to level off in future technologies, chip designs in general and interconnects in particular will require specialization to meet power and performance objectives.In this work, we make the observation that cache-coherent manycore server chips exhibit a duality in on-chip network traffic. Request traffic largely consists of simple control messages, while response traffic often carries cache-block-sized payloads. We present Cache-Coherence Network-on-Chip (CCNoC), a design that specializes the NoC to fit the demands of server workloads via a pair of asymmetric networks tuned to the type of traffic traversing them. The networks differ in their datapath width, router microarchitecture, flow control strategy, and delay. The resulting heterogeneous CCNoC architecture enables significant gains in power efficiency over conventional NoC designs at similar performance levels. Our evaluation reveals that a 4x4 mesh-based chip multiprocessor with the proposed CCNoC organization running commercial server workloads is 15-28% more energy efficient than various state-of-the-art singleand dual-network organizations.⋆

This paper presents an energy-efficient solar energy harvesting and sensing microsystem that harvests solar energy from a micro-power photovoltaic module for autonomous operation of a gas sensor. A fully integrated solar energy harvester stores the harvested energy in a rechargeable NiMH microbattery. Hydrogen concentration and temperature are measured and converted to a digital value with 12-bit resolution using a fully integrated sensor interface circuit, and a wireless transceiver is used to transmit the measurement results to a base station. As the harvested solar energy varies considerably in different lighting conditions, in order to guarantee autonomous operation of the sensor, the proposed area- and energy-efficient circuit scales the power consumption and performance of the sensor. The power management circuit dynamically decreases the operating frequency of digital circuits and bias currents of analog circuits in the sensor interface circuit and increases the idle time of the transceiver under reduced light intensity. The proposed microsystem has been implemented in a 0.18 µm complementary metal-oxide-semiconductor (CMOS) process and occupies a core area of only 0.25 mm2. This circuit features a low power consumption of 2.1 µW when operating at its highest performance. It operates with low power supply voltage in the 0.8V to 1.6 V range

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This paper presents a fully integrated, ultra-low power microsystem that is used for hydrogen gas sensing in an autonomous wireless sensor node. The proposed circuit harvests solar energy from a micro-power photovoltaic module to measure temperature and hydrogen concentration and transmits the measured value using wireless data transmission. A rechargeable NiMH microbattery is used to store harvested energy. Photovoltaic module charges this microbattery, using a highly area-and power-efficient power management circuit. In order to measure hydrogen concentration, conductance change of a miniaturized palladium nanowire sensor is measured and converted to a digital signal with 12-bit resolution, using an area-efficient readout circuit. The proposed microsystem has been implemented in a 0.18µm CMOS process and occupies a core area of only 0.47mm 2 . This circuit features a low current consumption of 200nA for power management circuit and an additional 1.1µA for sensor interface circuit. It operates with low power supply voltage in the 0.8V to 1.6V range.

This paper presents a fully integrated solar energy harvester for ultra-low power autonomous microsystems. This area-and power-efficient circuit harvests solar energy from a micro-power photovoltaic module to charge a rechargeable NiMH microbattery. As the harvested solar energy varies considerably in different lighting condition, the proposed circuit scales the power consumption and performance of the target microsystem, according to the harvested solar energy. Battery voltage is measured when battery is discharged by a high discharge current, to estimate harvested solar energy. Operating frequency and supply voltage of digital circuits and bias currents of analog circuits are reconfigured dynamically, based on measured battery voltage to optimize power-performance of the microsystem. This circuit occupies a core area of only 0.2mm 2 in a 0.18µm CMOS process and features a low power consumption of 390nW operating at its highest clock frequency.I.