Power Management of Flash Memory for Portable Devices ELG 4135, Fall 2006 Faculty of Engineering,...
Transcript of Power Management of Flash Memory for Portable Devices ELG 4135, Fall 2006 Faculty of Engineering,...
Power Management of Flash Memory for Portable Devices
ELG 4135, Fall 2006
Faculty of Engineering, University of Ottawa
November 1, 2006
Thayalan Selvam
Suganthan Vivekananthan
Thushitha Kanagaratnam
Outline
Introduction to Flash Memory Why power optimization? Dynamic Voltage Scaling Simulation Conclusion
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
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
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
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
Limitations on Power Optimization
Low power consumption Supply voltage Clock frequency Performance time Circuit delay Low cost
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
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
Our Contributions Literature search on various power
management algorithms Selected one Dynamic Voltage Scaling
algorithm: Dynamic Voltage Adjustment algorithm
We proposed a new version of existing dynamic voltage adjustment algorithm
The performance of the new algorithm is compared with the existing algorithm
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
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 first K tasks at high voltage (make sure that k is minimized)
end End
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 shortest K tasks at high voltage (make sure that k is minimized)
endEnd
Simulation Set Up
Vpp
Block Write
Block Erase
Power Consumption
Performance
Power Consumption
Performance
5 V375 mW
0.5 S250 mW
0.4 S
12 V540 mW
0.4 S480 mW
0.3 S 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)
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)
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
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.
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
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