Paper Info
Title
FlexWatts: A Power- and Workload-Aware Hybrid Power Delivery Network for Energy-Efficient Microprocessors
Abstract
Modern client processors typically use one of three commonly-used power delivery network (PDN) architectures: 1) motherboard voltage regulators (MBVR), 2) integrated voltage regulators (IVR), and 3) low dropout voltage regulators (LDO). We observe that the energy-efficiency of each of these PDNs varies with the processor power (e.g, thermal design power (TDP) and dynamic power-state) and workload characteristics (e.g., work-load type and computational intensity). This leads to energy-inefficiency and performance loss, as modern client processors operate across a wide spectrum of power consumption and execute a wide variety of workloads. To address this inefficiency, we propose FlexWatts, a hybrid adaptive PDN for modern client processors whose goal is to provide high energy-efficiency across the processor's wide range of power consumption and workloads. FlexWatts provides high energy-efficiency by intelligently and dynamically allocating PDNs to processor domains depending on the processor's power consumption and workload. FlexWatts is based on three key ideas. First, FlexWatts combines IVRs and LDOs in a novel way to share multiple on-chip and off-chip resources and thus reduce cost, as well as board and die area overheads. This hybrid PDN is allocated for processor domains with a wide power consumption range (e.g., CPU cores and graphics engines) and it dynamically switches between two modes: IVR-Mode and LDO-Mode, depending on the power consumption. Second, for all other processor domains (that have a low and narrow power range, e.g., the IO domain), FlexWatts statically allocates off-chip VRs, which have high energy-efficiency for low and narrow power ranges. Third, FlexWatts introduces a novel prediction algorithm that automatically switches the hybrid PDN to the mode (IVR-Mode or LDO-Mode) that is the most beneficial based on processor power consumption and workload characteristics. To evaluate the tradeoffs of PDNs, we develop and open-source PDNspot, the first validated architectural PDN model that enables quantitative analysis of PDN metrics. Using PDNspot, we evaluate FlexWatts on a wide variety of SPEC CPU2006, graphics (3DMark06), and battery life (e.g., video playback) workloads against IVR, the state-of-the-art PDN in modern client processors. For a 4 W thermal design power (TDP) processor, FlexWatts improves the average performance of the SPEC CPU2006 and 3DMark06 workloads by 22% and 25%, respectively. For battery life workloads, FlexWatts reduces the average power consumption of video playback by 11% across all tested TDPs (4W-50W). FlexWatts has comparable cost and area overhead to IVR. We conclude that FlexWatts provides high energy-efficiency across a modern client processor's wide range of power consumption and wide variety of workloads, with minimal overhead.
Year
DOI
Venue
2020
10.1109/MICRO50266.2020.00088
2020 53rd Annual IEEE/ACM International Symposium on Microarchitecture (MICRO)
Keywords
DocType
ISBN
FlexWatts,energy-efficient microprocessors,dynamic power-state,power-and workload-aware hybrid power delivery network,PDN architecture,motherboard voltage regulator,integrated voltage regulators,MBVR,IVR,low dropout voltage regulator,LDO,hybrid adaptive PDN,multiple on-chip resource,multiple off-chip resource,TDP processor,thermal design power processor,power 4 W to 50 W
Conference
978-1-7281-7384-9
Citations 
PageRank 
References 
0
0.34
35
Authors
8
Name
Order
Citations
PageRank
Jawad Haj-Yahya121.03
Mohammed Alser2173.19
Jeremie Kim326313.68
Lois Orosa4725.27
Efraim Rotem525811.37
Avi Mendelson651755.88
Anupam Chattopadhyay76315.06
Onur Mutlu89446357.40