With so much development for the Internet of Things (IoT) targeting battery-powered operation, it's no wonder that microcontroller vendors have been engaging in a game of low-power leapfrog with one another, vying for the title of best in low-power performance. But with the announcement of verified EEMBC ULPBench benchmark results for Ambiq Micro's Apollo MCU at ARM TechCon this week, that game may be all but won. The Cortex M4F-based Apollo MCU achieved twice the score of the prior title holder.
ULPBench is an industry-standard means of measuring MCU energy efficiency that mimics typical low-power system behavior. The benchmark works in conjunction with a standardized hardware device that monitors the MCU's energy consumption. Both the benchmark and monitoring device were developed by the Embedded Microprocessor Benchmark Consortium (EEMBC), which also validates vendor test results. According to EEMBC president Markus Levy, the benchmark calls for the MCU to perform 20k clock cycles of active work once a second and sleep for the remainder of that second, repeating the cycle multiple times to ensure accurate results. The benchmark score is 1,000 divided by the median value for average energy used during each of 10 benchmark cycles. A larger value therefore represents less energy consumed and because the benchmark counts clocks rather than using a fixed time interval, the results compensate for clock speed differences among processors.
Results posted on the EEMBC website show the prior leader in low power performance was the STMicroelectronics STM32L476RG MCU with a score of 187.7. Ambiq Micro held a public demonstration at ARM TechCon of its Apollo MCU achieving a whopping 377.5.