Supply Switching With Ground Collapse for Low-Leakage Register Files in 65-nm CMOS

Abstract

Power-gating has been widely used to reduce subthreshold leakage current. However, the extent of leakage saving through power-gating diminishes with technology scaling due to gate leakage of data-retention circuit elements. Furthermore, power-gating involves substantial increase of area and wirelength. A circuit technique called supply switching with ground collapse (SSGC) has recently been proposed to overcome the limitation of power-gating. The circuit technique is successfully applied to the register file of ARM9 microprocessor in a 1.2 V, 65-nm CMOS process, and the measured result is reported for the first time. The leakage current is reduced by a factor of 960 on average of 83 dies at 25 C, and by a factor of 150 at 85 C. Compared to a register file implemented in conventional power-gating, leakage current is cut by a factor of 2.2, demonstrating that SSGC can be a substitute for power-gating in nanometer CMOS.

Efficient Power Gating of SIMD Accelerators Through Dynamic Selective Devectorization in an HW/SW Codesigned Environment

“…Increase in the idle period helps the leakage control mechanism to save more energy. The proposed mechanism can work with any leakage control mechanism, such as power gating, SSGC [Kim et al 2010], and so forth. Moreover, the idea of increasing the idle period is general enough to be extended to other functional units as well.…”

“…As leakage is becoming a growing concern in the current microprocessor designs, several leakage control mechanisms have been studied [Hu et al 2004;Kim et al 2010;Tschanz et al 2003;Ye et al 1998]. All these mechanisms try to reduce leakage when the circuit is in an idle state.…”

“…Power gating [Hu et al 2004] consists of shutting down parts of the circuit by cutting their power supply by means of high-threshold header or footer transistors, called sleep transistors. Supply Switching with Ground Collapse (SSGC) [Kim et al 2010] is similar to power gating as this technique also cuts the power supply to the circuit. However, it is more effective than power gating in reducing leakage in data retention circuits.…”

“…Many leakage control techniques have been studied [Hu et al 2004;Kim et al 2010;Tschanz et al 2003;Ye et al 1998], power gating being one of the most prominent ones. Power gating cuts the supply voltage to the idle functional units, resulting in leakage energy savings.…”

Dynamic Selective Devectorization for Efficient Power Gating of SIMD Units in a HW/SW Co-Designed Environment

“…Power gating [9] consists of shutting down parts of the circuit by cutting their power supply by means of high threshold header or footer transistors. SSGC [11] is similar to power gating as this technique also cuts the power supply to the circuit. However, it is more effective than power gating in reducing leakage in data-retention circuits.…”