Power Profiling for Embedded Applications

8/3/2019 Power Profiling for Embedded Applications

1/13

321056

Power Profiling for

Embedded

ApplicationsJanuary 2009

Chris D. Lucero

Thermal MechanicalApplications EngineeringManager

Chakravarthy Akella

Sr. Thermal MechanicalEngineer

Intel Corporation


2/13

Power Profiling for Embedded Applications

2 321056

Executive Summary

Todays embedded customers are becoming more and more conscious of

how much power their platforms consume. In an effort to reduce overall

global power consumption and in turn minimize a businesss carbon

footprint, companies must optimize their hardware and software

computing solutions to run more efficiently. Intels Embedded and

Communications Group (ECG) developed a new power profiling kit which

can accurately measure a platforms total AC, DC, and component level

power consumption while running standard applications or benchmarks.

Armed with this data, embedded system designers can take advantage of

various power saving Intel architecture features to match the demands

put on their systems during peak and off-peak operation.

In an effort to reduce overall global power consumption and in turn

minimize a businesss carbon footprint, companies must optimize their

hardware and software computing solutions to run more efficiently.

Power profiling is a method used to measure actual power consumption of

the major components within a computing platform by running standard

applications and benchmarks. Multiple components rarely run

simultaneously at their maximum thermal design power TDP, hence this

procedure tends to provide a more realistic system power estimate and

avoid unwarranted conservatism. This paper describes steps in

implementing power profiling on an Intel architecture platform.

Power profiling is done in three main steps: computing the system AC

power, computing the system DC power and computing the component

power. The system AC power can be monitored using an AC power meter;

the DC power supply can be measured by employing a separate system


3/13


321056 3

breakout board. The breakout board introduces a lossless circuit between

the power supply and the motherboard by employing Hall Effect

transducers for the voltage rails of interest (I.E. 3.3V, 5V, 12V etc).

Component level power profiling is slightly more complicated since it

involves isolating all power sources the sources of power to a given

component and measuring the power consumed in each.


4/13


4 321056

Contents

Executive Summary ................................................................................................2Contents ...............................................................................................................4Introduction...........................................................................................................5The Need for Power Profiling.....................................................................................5

Tendency to Sum Up TDPs .....................................................................5For Power Management Implementation...................................................6

Advantages of Power Profiling To Customers...............................................................7How is Power Profiling Done?....................................................................................7

AC Power Measurement .........................................................................8DC Power Measurement.........................................................................8Component Power Measurement ...........................................................10

Conclusion...........................................................................................................11


5/13


321056 5

Introduction

System designers frequently need a tool or procedure that enables them totake real time platform power measurements. The number of ways in which

the power data can be used is endless. Power data collected can be used tocompare various platforms under a performance/watt scale. Armed with thisdata a system designer can pinpoint the inefficiencies of voltage regulators

and optimize the system or better utilize the various power saving features ofIntel architecture.

Power profiling is a method used to measure platform and component level

power while running standard applications or benchmarks. Intels latest toolsuite consists of a new power profiling kit comprising hardware and softwarewhich can be used to accurately measure power. The power profiling kit can

measure a platforms total AC, DC, and component level power consumptionwhile running standard applications or benchmarks.

Power data can be collected from real- life applications and this data can beused to compare various platforms from a power perspective. This data canalso help customers understand the amount of power their applications

consume compared to standard industry benchmarks.

System engineers can use power profiling data to optimize the system by

choosing correct components and identifying redundant components orfeatures on the board. The power savings using various Intel architecturefeatures such as C-States, P-States, and S-States can be determined and theplatforms can be optimized accordingly to extract full benefit of all the

features.

The Need for Power Profiling

Power profiling data is a valuable tool and can be used for a wide variety of

applications. This section explains where power profiling plays a key role inthe decision making process.

Tendency to Sum Up TDPs

Engineers tend to sum up TDPs of individual components to estimate theplatform power. Given that individual components never simultaneously run

at TDP, the summation of individual component TDPs will yield a veryconservative number. This summation method has been proven to be anincorrect approach. Power profiling can provide more realistic platform power

consumption numbers.


6/13


6 321056

Figure 1 shows how the power consumption of each component changes

running a specific application. The first set of bars show that when the Maxpower program1 is used, the CPU runs at 100% of its TDP, while the memoryand chipsets run at much lower power. On the other hand when a memory

intensive application is used the CPU is underutilized. However, no singleapplication can simultaneously exercise all components.

Figure 1. Multiple Components Never Sun at TDP Simultaneously

Max

Power

SW

SpecInt

SW

SpecFP

SW

Max

MCH

CPU

CP

U

CPU

CPU

CPU

TDP

Specified.

Memory

M

emory

M

em

ory

Memory

Memory

MCH

MCH

MCH

MCH

MCH

ICH

ICH

ICH IC

H

ICH

IO

Benchmark

CPU

Mem

ory

MCH

ICH

PercentofTDP(%)

100% of specified TDP

Max

Power

SW

Max

Power

SW

SpecInt

SW

SpecInt

SW

SpecFP

SW

SpecFP

SW

Max

MCH

Max

MCH

CPU

CPU

CP

U

CP

U

CPU

CPU

CPU

CPU

CPU

CPU

TDP

Specified.

TDP

Specified.

Memory

Memory

M

emory

M

emory

M

em

ory

M

em

ory

Memory

Memory

Memory

Memory

MCH

MCH

MCH

MCH

MCH

MCH

MCH

MCH

MCH

MCH

ICHICH

ICHICH

ICHICH IC

HICH

ICHICH

IO

Benchmark

IO

Benchmark

CPU

CPU

Mem

ory

Mem

ory

MCH

MCH

ICHICH

PercentofTDP(%)

100% of specified TDP

For Power Management Implementation

Todays embedded customers are becoming more power sensitive. Across the

industry, efforts are underway to reduce the overall power consumption and,in turn, minimize the carbon footprint. Companies need a tool to monitorpower consumption. With a power profiling tool the customers are able totest various configurations and optimize the system so that computing

solutions run more efficiently.

Each power management feature has tradeoffs that the customer should

evaluate. Power states such as C1, C6, C7 help the system consume very lowpower when the system is idle for a longer duration. However, the drawbackwith the low power states is latency. Deeper sleep states translate to more

power savings; the tradeoff is higher system latency. Power profiling toolslet the customers measure the power under various sleep states and thenmake an informed decision about such tradeoffs in their power management

solution.

1 Intels Max Power and Max MCH Programs are designed to exercise the CPU

and the chipset, respectively.


7/13


321056 7

Datacenter hosting is a significant cost concern for several embedded

customers. The operation cost of a datacenter is directly proportional to thenumber of leased racks. It is in the best interest of the customers to populate

the racks fully to realize the highest performance for the price. However, the

racks are not fully populated with servers due to power constraints. So, thereis a need to optimize server performance and power consumption to

maximize the server density of a rack. Several power management featuresare used to ensure that the power envelope for the rack does not exceed thespecified limit. Power profiling ensures that the power management features

like this can be implemented at a rack level.

Advantages of Power Profiling To

Customers

Power profiling has several benefits for the customers. This section identifiesseveral advantages of power profiling.

Measure the actual power vs calculating: power profiling gives theability to measure the power in a platform real time. Users can accurately

measure the total platform power rather than approximating the value byadding up the TDPs values.

Compare customer application with benchmark application: userscan compare the power consumed in their application against standard

benchmarks for an estimate of how their application compares to industrybenchmarks.

Compare platforms: power profiling can be a powerful tool in comparing

different platforms. The user can compare platforms between twogenerations to observe the benefits of moving to a newer architecture orcompare Intel architecture platforms with competitors to evaluate thebenefits of the Intel architecture.

Implement power management features: customers can take fulladvantage of Intel architectures power saving features and optimize

their system using the power profiling data. Each usage condition isunique; therefore, the customer can fine-tune the power saving featuresaccording to their usage models.

Obtain performance per watt data: To gauge the performance of a

platform, the performance per watt number is critical. Power profilingdata can be used along with the performance data to get an accurateperformance/watt number.

How is Power Profiling Done?

Power profiling at the system level is done in three steps:


8/13


8 321056

1. Compute AC power

2. Compute DC power

3. Compute component power

Intels latest power profiling test suite comprises an AC power measurementunit, a breakout board to measure DC power, and a DAQ and host system

with software to run the entire setup.

AC Power Measurement

System AC power can be measured using an AC power meter and a breakoutbox. The breakout box is connected to the wall (ex. 120V AC, 60HZ) and thepower supply is connected to breakout box. The breakout box feeds the

voltage and current signals to the AC power meter. Figure 2 shows the blockdiagram used of the AC power measurement.

Figure 2. AC Power Measurement

DC Power Measurement

A system breakout board can be used to measure the DC power in a system.The breakout board introduces a lossless circuit between the power supply

and the motherboard by employing Hall Effect transducers for all the rails,e.g. 3.3V, 5V, 12V.

For all system DC power measurements, a lossless Hall Effect transducer is

used on every rail. The transducer is supplied with a 5V DC power supply andthe transducer produces an output voltage proportional to the current in thecircuit. DAQ calculates the current with the help of linear relationship of

Voltage and Current. This procedure of measurement of current is almostlossless as the transducer does not induce any voltage drop in the circuit.

AC Power Meter

Breakout box


9/13


321056 9

Figure 3. Current Measurement Transducer

Intels Embedded and Communications Group (ECG) has designed a breakout

board using a series of current transducers to measure the system DC power.The breakout board can accept input from the power supply, such as from 24pin, 8 pin, 4 pin connectors. The breakout board senses the current and then

feeds the various rails into the printed circuit board.

Figure 4. Breakout Board

DC power is the actual power that the system consumes. The efficiency of the

power supply can be computed by comparing the system AC power andsystem DC power. The power supply efficiency is a useful tool for selectingthe most efficient power supplies for the system.

0V V out

Power supply to thetransducer, +5V

DC, lossless

3.3 V

P/S

3.3 V


10/13


10 321056

Component Power Measurement

The component level power measurement is the most complicated step inpower profiling. To perform component level power measurements, a

component must be selected and all the rails supplying power must beisolated. In several cases components share common power planes. In suchcases the power to the component cannot be isolated. The flowchart in Figure

5shows the steps to perform component level power measurement.

Figure 5. Flowchart to Explain Component Level Power Measurement

Precautions to observe when power profiling:

For linear regulators with less than 4A output current, use a series2W+ metal film power resistor in a 1812 package.

For linear regulators with 4A or more of output current, use a halleffect or transducer (LTS-25NP) placed in series with the output.

For single phase switching buck regulators, use a transducer on theoutput side.

For multiphase buck regulators, use a transducer on the input side of

the voltage regulator. A two-step measurement approach is:


11/13


321056 11

Step 1: Measure the VRs conversion efficiency and record this data for

future reference. This is achieved with a CPU_VTT, Memory_VTT or aDC_Electronic load for loads without a supported VTT.

Step 2: During power profiling measurement, measure the input side andreference the collected data in step 1 to extrapolate the output current.

Component level power measurement is usually done for key components onthe motherboard e.g. CPU, chipsets and memory. Usually other componentsare on a shared power plane and very difficult to isolate.

Conclusion

Power Profiling is a technique that helps system designers make informeddecisions and optimize the features available on the platform.

The power profiling tool can be used for a wide variety of applications from

comparing different platforms to optimizing the power management featureson a platform. This paper provided details on the three steps in power

profiling (system AC, system DC and component level power measurement).

The new tools and techniques from Intel offer several benefits and

advantages. In summary, Intels customers need a solution for real timeplatform power measurements. The power profiling system provides such asolution.


12/13


12 321056

Chris D. Lucero is a Thermal Mechanical Applications Managerwith Embedded and Communications Group.

Chakravarthy Akella is a Sr. Thermal Mechanical Engineer withEmbedded and Communications Group.

Acronyms

TDP Thermal Design Power - It is the recommended designpoint for thermal solution power dissipation.


13/13


321056 13

INFORMATION IN THIS DOCUMENT IS PROVIDED IN CONNECTION WITH INTEL PRODUCTS.NO LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUALPROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. EXCEPT AS PROVIDED IN INTELS TERMSAND CONDITIONS OF SALE FOR SUCH PRODUCTS, INTEL ASSUMES NO LIABILITYWHATSOEVER, AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY, RELATING TO

SALE AND/OR USE OF INTEL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TOFITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT,COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. Intel products are not intended for usein medical, life saving, or life sustaining applications.

Intel may make changes to specifications and product descriptions at any time, without notice.

This paper is for informational purposes only. THIS DOCUMENT IS PROVIDED "AS IS" WITH NO

WARRANTIES WHATSOEVER, INCLUDING ANY WARRANTY OF MERCHANTABILITY,

NONINFRINGEMENT, FITNESS FOR ANY PARTICULAR PURPOSE, OR ANY WARRANTY OTHERWISE

ARISING OUT OF ANY PROPOSAL, SPECIFICATION OR SAMPLE. Intel disclaims all liability, including

liability for infringement of any proprietary rights, relating to use of information in this specification.

No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted

herein.

Intel, the Intel logo, Intel. leap ahead. and Intel. Leap ahead. logo, are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the

United States and other countries.

*Other names and brands may be claimed as the property of others.

Copyright 2008 Intel Corporation. All rights reserved.

Power Profiling for Embedded Applications

Documents