A programmable resistive power grid for post-fabrication flexibility and energy tradeoffs

Abstract

This paper explores the benefits of splitting a monolithic power gate transistor into parallel, independently controlled, variable weighted power gates to provide programmable post-fabrication power grid resistance. This power gate topology creates energy saving opportunities by providing adjustable localized voltages during active modes and reducing leakage current in idle blocks while retaining data. Measurements show over 30% active energy savings per operation and 90% savings in idle current with retention. A modeling flow for a resistive power grid was also developed that demonstrates the effectiveness of this approach in a Bulldozer processor core.

Optimal power switch design methodology for ultra dynamic voltage scaling with a limited number of power rails

“…Adjustable DC-DC converters tend to have limited efficiency over broad output voltage ranges, and they take hundreds of micro-seconds to switch between different supply levels especially in the nearthreshold regime [6]. An alternative implementation approach called local voltage dithering (LVD) uses header power switches to connect circuit blocks to one of the several power supply rails, thereby allowing for faster switching [7] [8]. The LVD approach supports application of fine-grained ultra DVS (UDVS) down to the near-threshold regime and to smaller internal circuit blocks.…”