Low Power Blogs

I noticed some very interesting news last week, widely reported in the technical press, and you can find the source press release here. In a nutshell, the Embedded Microprocessor Benchmark Consortium (EEMBC) has formed a group to look at benchmarks for ultra low power microcontrollers. Initially chaired by Horst Diewald, chief architect of MSP430^TM microcontrollers at Texas Instruments, the group's line-up is an impressive "who's who" of the microcontroller space, including Analog Devices, ARM, Atmel, Cypress, Energy Micro, Freescale, Fujitsu, Microchip, Renesas, Silicon Labs, STMicro, and TI.

As the press release explains, unlike usual processor benchmark suites which focus on performance, the ULP benchmark will focus on measuring the energy consumed by microcontrollers running various computational workloads over an extended time period. The benchmarking methodology will allow the microcontrollers to enter into their idle or sleep modes during the majority of time when they are not executing code, thereby simulating a real-world environment where products must support battery life measured in months, years, and even decades.

Processor performance benchmarks seem to be as widely criticized as EPA fuel consumption figures for cars - and the criticism is somewhat related. There is a suspicion that manufacturers can tune the performance for better test results, rather than better real-world performance. On the face of it, the task to produce meaningful ultra low power benchmarks seems even more fraught with difficulties. For a start, there is a vast range of possible energy profiles - different ways that computing is spread over time - and a plethora of low power design techniques available to optimize the system for the set of profiles that particular embedded system is likely to experience. Furthermore, you could argue that, compared with performance in a computer system, energy consumption in an ultra low power embedded system has less to do with the controller itself and more to do with other parts of the system like the memories and mixed-signal real-world interfaces.

EEMBC cites that common methods to gauge energy efficiency are lacking in growth applications such as portable medical devices, security systems, building automation, smart metering, and also applications using energy harvesting devices. At Cadence, we are seeing huge growth in these areas which, along with intelligence being introduced into all kinds of previously "dumb" appliances, is becoming known as the "Internet of Things." Despite the difficulties, with which the parties involved are all deeply familiar, I applaud this initiative. While it may be difficult to get to apples-to-apples comparisons for energy consumption in these applications, most of the time today we don't even know where the grocery store is. If the EEMBC effort at least gets us to the produce department, we're going to be better off.

Pete Hardee