Superrange wide operational range power delivery design for both stv and ntv computing
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SuperRange: Wide Operational Range Power Delivery Design for both STV and NTV Computing. Xin He, Guihai Yan, Yinhe Han, Xiaowei Li Institute of Computing Technology, Chinese Academy of Sciences. The need of wide operation range.

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SuperRange: Wide Operational Range Power Delivery Design for both STV and NTV Computing

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Superrange wide operational range power delivery design for both stv and ntv computing

SuperRange: Wide Operational Range Power Delivery Design for both STV and NTV Computing

Xin He,

Guihai Yan, Yinhe Han, Xiaowei Li

Institute of Computing Technology, Chinese Academy of Sciences


The need of wide operation range

The need of wide operation range

  • Microprocessor’s supply voltage range has been gradually increasing in these year

    • Intel Pentium Processor has a supply voltage range from 0.9V to 1.5V to support DVFS

    • Intel Sandy Bridge Processor requires a higher than nominal voltage to boost performance

Turbo

DVFS

Intel PentiumProcessor

Turbo Boost in Intel Sandy Bridge

0.9V

1.5V

(66.7%)


The need of wide operation range1

The need of wide operation range

  • Near Threshold Computing: set supply voltage to a value near to transistor’s threshold voltage (0.4V-0.6V)

Turbo

DVFS

Intel ISSCC2012

NTC

0.28V-1.2V

Future Microprocessor has wide supply voltage range. Brings challenges to power delivery design


Background of power delivery design

Background of Power Delivery Design

  • Voltage regulator is key to deliver power at a specified voltage level

    • Linear regulator-LDO

    • Switching regulator

      • Buck regulator(Off-VR)

      • Switch capacitor regulator(On-VR)

Buck Regulator

Switch Capacitor Regulator


Power conversion efficiency characteristics

Power Conversion Efficiency Characteristics

  • VRs are delivering power to wide operational range cores

High PCE

High PCE

  • Off-VR:

    • High switching loss

  • On-VR:

    • Narrow optimal region

  • LDO-VR:

    • Limited efficiency

Low PCE

Low PCE

Conventional design can’t meet the need of wide voltage range


C ontribution

Contribution

  • Explore the design space of wide operational range power delivery design

  • Propose SuperRange, a wide operation range power delivery scheme

  • Present a VR aware power management algorithm to maximize performance under given power budget


Design space exploration

Design space exploration

  • Explore three optional design

    • Off-VRs

      • Two Off-VR evenly located

    • Off-VR + LDO-VR

      • An Off-VR serves as an frontend

    • Off-VR + On-VR

      • Off-VR delivers to STV and On-VR to NTV


Option 1 off vrs scheme

Option 1:Off-VRs scheme

  • Loss in Off-VRs

dominants!

20%

Cross 10%


Option 2 ldo vr scheme

Option 2:LDO-VR scheme

  • In LDO-VR

    • PCE is limited by the ratio of output voltage to input voltage

      • PCE is lower than 30% when delivering to NTV region


Option 3 off vr on vr scheme

Option 3:Off-VR + On-VR scheme

  • Using Off-VR to deliver to STV region

  • Two step voltage conversion

  • How to decide intermediate voltage

1) Fixed intermediate voltage

  • Off-VR delivers fixed output voltage 2V

  • Tuning On-VR paramsto achieve further conversion

    • PCE of Off-VRs is high

    • On-VR couldn’t deliver to all NTV levels at high PCE


Off vr on vr scheme

Off-VR + On-VR scheme

2) Using varied intermediate voltage

  • Off-VR delivers to varied voltage levels

    • Duty cycle tuning

  • On-VR further step these intermediate values to 0.4V-0.6V

  • Pros:

    • On-VR has high PCE(around 80%)

  • Cons:

    • The PCE of Off-VR remains low because of small load current


Proposed superrange design

Proposed SuperRange Design

  • Multi-phase Off-VR provides an opportunity to improve load current, thus PCE get improved

    • Modern Off-VR can dynamically change number of working phases

  • Decreasing the number of working phases would increase output ripple

    • 1.5uH inductor is big enough

      to reduce the ripple with

      acceptable area overhead


Superrange overview

SuperRange Overview

  • Supporting STV

    • Voltage conversion to STV is performed by Off-VR

  • Supporting NTV

    • Two step conversion.

      • Off-VR sets to single working phase

      • On-VR achieves further conversion(e.g. 3:1)


Vr aware power management algorithm

VR aware power management algorithm

  • Maximize performance under given power budget

    • Find optimal core counts and VF setting

More cores, Low voltage

Few cores, High voltage

  • PCE with varying load current

    • Although low voltage improve app power efficiency, it degrades the PCE


Algorithm

Algorithm

  • Determine voltage setting candidates

    • Computes the total powers when all cores are active at each voltage level

    • Selects the lowest voltage () and the highest voltage ()

  • Determine active core count

    • Calculate max active core count at voltage and get corresponding performance

    • Compare the performance with and make decisions


Experimental setup

Experimental Setup

  • Target processor characteristics

  • Multicore processor consists 16 ALPHA cores which has 9 power state

    • (1.2v, 1.9GHz), (1.1v, 1.7GHz), (1.0v, 1.5GHz)… (0.4v, 0.3GHz)

  • 32MB LLC, distribute directory-based MESI

  • On chip interconnection: mesh + router

  • Voltage regulator model

    • Single topology (3 to 1) Switch capacitor voltage regulator

    • Buck voltage regulator like TI TPS 54912


  • Power conversion efficiency

    Power Conversion Efficiency

    SuperRange combines the advantages of Off-VR and On-VR and

    exhibits high PCE over the entire voltage range


    Comparison

    Comparison

    • Performance comparison in power-constrait system

    • SuperRange outperforms LDO scheme by 50% and

    • Off-VR scheme by 30%


    Comparison1

    Comparison

    • Maximum achievable performance comparison under shrinking power budget

    • On average, SuperRange achieve 52% and 170% higher PCE

    • than Off-VR and LDO-VR scheme.


    Conclusion

    Conclusion

    • Power delivery design for wide operational range is an important issue

    • Explore the optional power delivery design scheme

    • The proposed SuperRange scheme achieves high PCE over the entire operational range

    • Propose a VR aware power management algorithm


    Superrange wide operational range power delivery design for both stv and ntv computing

    • Thank You for Your Attention

    • Question?


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