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Power Management of Flash Memory for Portable Devices. Thayalan Selvam Suganthan Vivekananthan Thushitha Kanagaratnam. ELG 4135, Fall 2006 Faculty of Engineering, University of Ottawa November 1, 2006. Outline. Introduction to Flash Memory Why power optimization?

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Power management of flash memory for portable devices l.jpg

Power Management of Flash Memory for Portable Devices

Thayalan Selvam

Suganthan Vivekananthan

Thushitha Kanagaratnam

ELG 4135, Fall 2006

Faculty of Engineering, University of Ottawa

November 1, 2006


Outline l.jpg
Outline

  • Introduction to Flash Memory

  • Why power optimization?

  • Dynamic Voltage Scaling

  • Simulation

  • Conclusion


Flash memory l.jpg
Flash Memory

  • Non-volatile data storage devices

  • Storage of trapped electrons in cells

  • Cells have different logical functions: NOR or NAND

  • NOR flash memory:- Faster read time longer erase and write times

  • NAND flash memory:- Longer read time Faster erase and write times


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Usage of Flash Memory

  • Computer's BIOS chip

  • Digital cameras

  • Mp3 players

  • Memory Stick

  • PCMCIA Type I and Type II memory cards

  • PDA


Advantages of flash memory l.jpg
Advantages of Flash Memory

  • Maintain stored information without power source

  • High storage capacity and compatibility

  • No physical disk to spun as in hard disks

  • High processing speed:-Virtually the speed is same as light’s speed. Limiting factor is USB 2.0

  • Compact size:- 2mm to 3mm in width


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Why Power Optimization ?

  • Demand for portable electronics devices have increased

  • Power consumption is major obstacle in any mobile portable devices.

  • Main task to maintain low power consumption

  • Low power increases the performance and makes the devices durable


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Limitations on Power Optimization

  • Low power consumption

  • Supply voltage

  • Clock frequency

  • Performance time

  • Circuit delay

  • Low cost



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Power Optimization Algorithms

  • Dynamic Voltage Scaling

  • Static Voltage Scaling

  • Voltage Clock Scaling


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Dynamic Voltage Scaling Algorithm

  • Allows devices to change voltage and speed

  • Uses different voltage level for program, write and erase

  • Uses high voltage when the work load is high

  • Uses low voltage when the work load is low


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Advantages of Dynamic Voltage Scaling Algorithm

  • Advanced electronic chips allows to have different voltage levels in devices

  • Intelligence power management allows to lengthen the operational time by operating the devices at low power level, whenever possible

  • Save the battery power


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Our Contributions

  • Literature searchon various power management algorithms

  • Selected one Dynamic Voltage Scaling algorithm:Dynamic Voltage Adjustment algorithm

  • We proposeda new version of existing dynamic voltage adjustment algorithm

  • Theperformanceof the new algorithm is compared with the existing algorithm


Dynamic voltage adjustment dva algorithm l.jpg
Dynamic Voltage Adjustment (DVA) Algorithm

  • NOR Flash Memory: Block read uses constant voltage level. Power management is required only for write and erase operations

  • Each tasks have deadline time

  • This algorithm based on Earliest Deadline First (EDF) algorithm. That is earliest deadline tasks are scheduled very first

  • First K tasks are operated at high voltage level and rest of the tasks are at low voltage level

  • This algorithm make sure that K is minimized


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DVA (Cont’d.)

  • Let S = {R1, R2 …… Rn} be the pending request for flash memory and are arranged according to its deadline T1, T2,…Tn. Here, T1 < T2 <…Tn

  • pseudo code

    For i=1:n

    Schedule task Ri at low voltage

    Find total time

    if total time > Ti

    adjust firstK tasks at high voltage (make sure that k is minimized)

    end

    End


New version of dva l.jpg
New version of DVA

  • Pseudo code of proposed algorithm

    For i=1:n

    Schedule task Ri at low voltage

    Find total time

    if total time > Ti

    adjust shortestK tasks at high voltage (make sure that k is minimized)

    end

    End


Simulation set up l.jpg
Simulation Set Up

  • Considered NOR Flash memory:

    - Read time is constant. Write and Erase are considered

  • Block Size: 64 kb

  • Two levels of operating voltages: 5V and 12V


Simulation results voltage level l.jpg
Simulation Results (Voltage Level)

  • First 5 tasks are operated at high voltage

  • Rest of the tasks are operated at low voltage

  • This algorithms make sure that the number of high voltage tasks are minimized

  • Proposed algorithm set shortest k tasks at high voltage


Simulation results power consumption l.jpg
Simulation Results (Power Consumption)

  • This graph compares the power consumption of the algorithms

  • Graph clearly indicates the performance of the DVA (Dynamic Voltage Adjustment) algorithm and the proposed algorithm

  • However, proposed algorithm have 6.475% improvement compare to existing DVA algorithm


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Conclusion

  • Dynamic Voltage Adjustment algorithm is considered

  • The simulation results shows efficiency of the power management algorithm

  • Dynamic Voltage Adjustment algorithm is useful in the implementation of portable devices which saves battery power

  • We gained a good knowledge in various power management algorithms.


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Future work!

  • In this context, we considered heuristic approaches for power management and therefore the solution is near optimum

  • Explore efficient optimization tools to find exact optimal solution

  • Online arrival of tasks can be incorporated

  • Consider multi voltage levels. (This project we have considered two voltage levels). However, voltage levels cannot be increased as many since the electronic circuit’s limitations


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References

  • [1] Tanzawa T, Takano Y, Taura T, Atsumi S. “A Novel Bit-Line Direct- Sense Circuit that uses a feedback system for High-Speed Flash Memory.” Research Institute of Electrical Communication, Tohoku University, Japan. January 2006

  • [2] Li-Pin Chang, Tei Wei Kuo, Shi-Wu Lo. “ A Dynamic- Voltage- Adjustment in reducing the power consumption of flash memory for portable devices.” Taipei,Taiwan.

  • [3] Yehua Du, Ming Cai, Jinxiang Dong. “Dynamic Voltage Scaling of Flash Memory Storage Systems for Low-Power Real-Time Embedded Systems.” Zhejiang University, Hangzhou, China


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Thank You

  • Special Thanks to Dr. Habash and TA’s for help and supports.

    Questions?????


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