Abstract:

As microprocessors become increasingly interconnected, the power consumed by the interconnection network can no longer be ignored. It will be the key limiter to system scalability as interconnection networks take up an increasingly significant portion of system power with process technology scaling down and system frequencies and communication bandwidth scaling up.

This thesis explores the power-performance of interconnection networks across multiple levels, from circuits to router microarchitecture, to network architecture, from single chip networks to networks that span multiple chassis. As is well known, there are three main components of power consumption: leakage power, dynamic power and DC power (for analog circuits). This thesis addresses all three components, through proposing new power models, novel power management techniques, inventing power-aware circuits, demonstrating the potential impact on interconnection network power-performance.

Leakage power modeling and optimization is first studied in this thesis. As technology scales down, and threshold voltage reduces further, leakage power contribution becomes comparable to that of dynamic power. It is no longer negligible. In order to characterize the leakage power consumption, an architectural leakage power modeling methodology that achieves 95-98% accuracy against HSPICE estimates is proposed. When applied to interconnection networks, combined with previous proposed dynamic power models, it shows router buffers to be a prime candidate for leakage power optimization. A suite of policies is thus proposed for power-aware buffers and the impact of various circuits mechanisms on these policies was explored. Simulations show power-aware buffers saving up to 96:6% of total buffer leakage power with negligible performance degradation.

Next, the design space of opto-electronic networked system is explored focusing on the optimization of the dynamic and DC power consumption. Dynamic power and DC power has always been key concerns of both circuit designers and system architects. Moreover, with demand for link bandwidth increasing, optical links are being considered as a replacement for electrical links in interconnection network. As a result, the power dissipation of optical links is becoming as critical as their speed. So we explored alternative ways of realizing high speed opto-electronic interconnection networks and investigate the characteristics of different link components. Circuit and network mechanisms are then proposed to realize power-aware optical links--links whose power consumption can be tuned dynamically in response to changes in network traffic. Power-control policies along with the power characterization of link circuitry are incorporated into a detailed network simulator to evaluate the performance cost and power savings of building power-aware opto-electronic networked systems. Simulation results show that up to 4X savings in power consumption can be achieved with the proposed power-aware opto-electronic network.

Finally, opto-electronic transceiver front-ends (laser driver and transimpedance amplifier) are designed for power-aware opto-electronic networked system. In order to realize power-aware opto-electronic link, link components must be specially designed to adapt to a wide range of supply voltages, while delivering high bandwidth and low power. Supply voltage Vdd of our transceiver front-ends fabricated in 130nm CMOS process can scale from 1.2V to 0.6V with power consumption scaling faster than [Special characters omitted.] . As a result, the transimpedance amplifier consumes only 2.2mW at 1.2V and 0.4mW at 0.7V with achievable transimpedance more than 57dB?, while still maintaining high bandwidth from 10 to 4Ghz. The laser driver achieves similar performance across the wide range of supply voltage. To the best of our knowledge, this is the first design of an adaptive supply opto-electronic transceiver front-end, demonstrating the feasibility of a complete power-aware link. Moreover our design is able to ensure low power consumption while delivering high gain and bandwidth.