We consider active leakage power dissipation in FPGAs and present a "no cost" approach for active leakage reduction. It is well-known that the leakage power consumed by a digital CMOS circuit depends strongly on the state of its inputs. Our leakage reduction technique leverages a fundamental property of basic FPGA logic elements (look-uptables) that allows a logic signal in an FPGA design to be interchanged with its complemented form without any area or delay penalty. We apply this property to select polarities for logic signals so that FPGA hardware structures spend the majority of time in low leakage states. In an experimental study, we optimize active leakage power in circuits mapped into a state-of-the-art 90nm commercial FPGA. Results show that the proposed approach reduces active leakage by 25%, on average.

Power optimization is of growing importance for FPGAs in nanometer technologies. Considering dual-Vdd technique, we show that configurable power supply is required to obtain a satisfactory performance and power tradeo#. We design FPGA circuits and logic fabrics using configurable dualVdd and develop the corresponding CAD flow to leverage such circuits and logic fabrics. We then carry out a highly quantitative study using area, delay and power models obtained from detailed circuit design and SPICE simulation in 100nm technology. Compared to single-Vdd FPGAs with optimized Vdd level for the same target clock frequency, configurable dual-Vdd FPGAs with full and partial supply programmability for logic blocks reduce logic power by 35.46% and 28.62% respectively and reduce total FPGA power by 14.29% and 9.04% respectively. To the best of our knowledge, it is the first in-depth study on FPGAs with configurable dual-Vdd for power reduction.

The continuing increase in FPGA size and complexity and the emergence of sub-100nm technology have made FPGA power consumption, both dynamic and static, an important design consideration. In this work, we propose a programmable dual-VDD architecture in which the supply voltage of the logic blocks and routing blocks are programmed to reduce power consumption by assigning low-VDD to non-critical paths in the design, while assigning high-VDD to the timing critical paths in the design to meet timing constraints. We evaluate the e#ectiveness of different VDD assignment algorithms and architectural implementations. Our

This paper studies power modeling for Field Programmable

Power is an increasingly important design constraint for FP-GAs in nanometer technologies. Because interconnect power is dominant in FPGAs, we design Vdd-programmable interconnect fabric to reduce FPGA interconnect power. There are three Vdd states for interconnect switches: high Vdd, low Vdd and power-gating. We develop a simple design flow to apply high Vdd to critical paths and low Vdd to non-critical paths and to power gate unused interconnect switches. We carry out a highly quantitative study by placing and routing benchmark circuits in 100nm technology to illustrate the power saving. Compared to single-Vdd FPGAs with optimized but non-programmable Vdd level for the same target clock frequency, our new FPGA fabric on average reduces interconnect power by 56.51 % and total FPGA power by 50.55%. Due to the highly low utilization rate of routing switches, majority of the power reduction is achieved by power gating unused routing buffers. In contrast, recent work that considers Vdd programmability only for logic fabric reduces total FPGA power merely by 14.29%. To the best of our knowledge, it is the first in-depth study on Vdd programmability for FPGA interconnect power reduction. 1.

Vdd-programmable FPGAs have been proposed recently to reduce FPGA power, where Vdd levels can be customized for different circuit elements and unused circuit elements can be power-gated. In this paper, we first develop an accurateFPGApowermodelandthendesignnovelVddprogrammable interconnect switches with minimum number of configuration SRAM cells. Applying our power model to placed and routed benchmark circuits, we evaluate Vddprogrammable FPGA architecture using the new switches. The best architecture in our study uses Vdd-programmable logic blocks and Vdd-gateable interconnects. Compared to the baseline architecture similar to the leading commercial architecture, the best architecture reduces the minimal energy-delay product by 44.14 % with 48 % area overhead and 3 % SRAM cell increase. Our evaluation results also show that LUT size 4 always gives the lowest energy consumption while LUT size 7 always leads to the highest performance for all evaluated architectures.

To reduce power, Vdd programmability has been proposed recently to select Vdd-level for interconnects and to powergate unused interconnects. However, Vdd-level converters used in the Vdd-programmable method consume a large amount of leakage. In this paper, we develop chip-level dual-Vdd assignment algorithms to guarantee that no low-Vdd interconnect switch drives high-Vdd interconnect switches. This removes the need of Vdd-level converters and reduces interconnect leakage and interconnect device area by 91.78% and 25.48%, respectively. The assignment algorithms include power sensitivity based heuristics with implicit time slack allocation and a linear programming (LP) based method with explicit time slack allocation. Both first allocate time slack to interconnects with higher transition density and assign low-Vdd to them for more power reduction. Compared to the aforementioned Vdd-programmable method using Vdd-level converters, the LP based algorithm reduces interconnect power by 65.13 % without performance loss for the MCNC benchmark circuits. Compared to the LP based algorithm, the sensitivity based heuristics can obtain slightly smaller power reduction but run 4X faster.

A methodology for supporting dynamic voltage scaling (DVS) on commercial FPGAs is described. A logic delay measurement circuit (LDMC) is used to determine the speed of an inverter chain for various operating conditions at run time. A desired LDMC value, intended to match the critical path of the operating circuit plus a safety margin, is then chosen; a closed loop control scheme is used to maintain the desired LDMC value as chip temperature changes, by automatically adjusting the voltage applied to the FPGA. We describe experiments using this technique on various circuits at different clock frequencies and temperatures to demonstrate its utility and robustness. Power savings between 4% and 54 % for the VINT supply are observed.

We propose a new programmable FPGA routing switch that can operate in three different modes: high-speed, low-power or sleep. High-speed mode offers similar power and performance to a traditional routing switch. In low-power mode, power is reduced at the expense of speed. Leakage power is reduced by 36-40 % in low-power vs. high-speed mode (on average); dynamic power is reduced by up to 28%. Leakage power in sleep mode is 61 % lower than in high-speed mode. The applicability of the new switch is motivated through an analysis of timing slack in industrial FPGA designs. Specifically, we show that a considerable fraction of routing switches may be slowed down (operate in low-power mode), without impacting overall design performance. I.

Field programmable gate arrays (FPGAs) with supply voltage (Vdd) programmability have been proposed recently to reduce FPGA power, where the Vdd-level can be customized for FPGA circuit elements and unused circuit elements can be power-gated. In this paper, we first design novel Vdd-programmable and Vdd-gateable interconnect switches with minimal number of configuration SRAM cells. We then evaluate Vdd-programmable FPGA architectures using the new switches. The best architecture in our study uses Vdd-programmable logic blocks and Vdd-gateable interconnects. Compared to the baseline architecture similar to the leading commercial architecture, our best architecture reduces the minimal energy-delay product by 54.39 % with 17 % more area and 3 % more configuration SRAM cells. Our evaluation results also show that LUT size 4 gives the lowest energy consumption, and LUT size 7 leads to the highest performance, both for all evaluated architectures.