Customer SolutionsMeasuring the Power Cost of Processor Performance Using EEMBC EnergyBench and NI LabVIEW
Author(s):Markus Levy, Embedded Microprocessor Benchmark Consortium
Industry:Energy/Power, Semiconductor
Product:Data Acquisition, LabVIEW
The Challenge:Developing a system that designers can use in conjunction with performance benchmarks set by EEMBC to determine how efficiently processors use energy while performing certain tasks.
The Solution:Standardizing on National Instruments LabVIEW graphical development software and data acquisition hardware to develop EnergyBench, which provides data on a processor’s energy consumption according to EEMBC’s performance benchmarks.
The Embedded Microprocessor Benchmark Consortium, or EEMBC, is a consortium of silicon, IP, and instrument vendors that was formed in 1997 to develop meaningful performance benchmarks for hardware and software used in embedded systems. Power efficiency is becoming an increasingly important product feature, but the methods for measuring consumption vary greatly. For instance, more efficient power use can increase the run times for portable devices, making it possible to use smaller batteries, reduce overall product size, and facilitate better thermal management. Processor vendors typically have their own power measurement methods, making it nearly impossible to make accurate comparisons among competing vendors. They usually offer “typical” power specifications on product datasheets, but different companies use different workloads to measure power consumption. The problem of interpreting these values is exacerbated when designers attempt to compare processor cores for system-on-chip implementations. As a solution to this problem, EEMBC developed EnergyBench, which can be used in conjunction with EEMBC’s performance benchmarks to determine how efficiently various processors use energy while carrying out a series of standardized, application-focused tasks. By using a standard metric for energy consumption that is directly tied to a standard set of performance tests, designers can compare the performance and energy of devices from multiple vendors and select the processors that best fit their needs for a given application and energy budget. We had to consider several factors when developing EnergyBench. Because EEMBC is an industry-standard consortium, we needed to create a comparison methodology that would be applicable for any processor vendor or system designer. In other words, the methodology needed to be portable across a wide range of processor platforms. Furthermore, the methodology needed to be as automated as possible to ensure reliable, repeatable, and consistent results. Once that was accomplished and agreed to by EEMBC’s members, we turned to National Instruments software and hardware to address additional obstacles. Having an inexpensive energy/power measuring framework was vital to completion of the project. We considered other solutions ranging from simple current meters to complex oscilloscopes. A simple current meter would have been inexpensive, but would have been costly in terms of engineering resources required to ensure consistent measurement techniques. On the other hand, an oscilloscope would have provided very accurate results, but would have been too costly. The combination of National Instruments LabVIEW software and Data Acquisition hardware provided an inexpensive and easily controllable system. Another critical feature was having a semi-automated methodology to ensure that all users could run the tests in a similar manner. With LabVIEW, we were able to develop an entire test environment and then ship an executable program that would run the same for everyone. And while many platforms will potentially require modifications to the energy measurement setup, LabVIEW can easily modify the system to accommodate these modifications. Furthermore, some engineers may choose data acquisition cards with faster sampling rates, which can easily be interchanged using NI components. The resulting product, EnergyBench, provides data on how much energy a processor consumes when running a real application workload and not just arbitrarily chosen test vectors. An EEMBC-certified Energymark score is an optional metric that a device manufacturer may choose to supply in conjunction with certified scores for device performance as a way of indicating a processor’s efficient use of power and energy. Besides providing design engineers with comparable information regarding energy consumption, EnergyBench gives designers insights into the power budget “cost” of a device’s performance by deriving a performance/energy number using the consolidated performance score in each benchmark suite. For example, EnergyBench makes it possible to calculate a “netmarks per joule" score for devices tested against EEMBC’s networking benchmarks, or a “telemarks per joule” score for devices tested against the consortium’s telecomm benchmarks. For more information, contact: Markus Levy President Embedded Microprocessor Benchmark Consortium Phone: 530-672-9113 Fax: 530-672-9439 E-mail: markus@eembc.org; markus@multicore-association.org Web: www.eembc.org
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