Benchmarking with Coremark

Jack Ganssle

January 22, 2013

Jack Ganssle

Scores (www.coremark.org/benchmark/index.php?pg=benchmark) are expressed as raw CoreMark, CoreMark/MHz (more interesting to me), and CoreMark/Core (for multicore devices). There are two types of results--those submitted from vendors, and those certified by EEMBC's staff (for a charge).

Results range from 0.03 CoreMark/MHz for a PIC18F97J60 to 168 for a Tilera TILEPro64 running 64 threads. The single-threaded max is 5.1 for a Fujitsu SPARK64V(8).

But away from speed demons like Pentium-class or SPARC machines, the highest score is for Atmel's SAM4S16CAU--a Cortex M4 device--which notches in at 3.38 CoreMark/MHz. That beats out a lot of high-end devices.

Clock rates do matter, and while the Intel Core i5 gets a score of 5.09 CoreMark/MHz, its raw result, at 2,500 MHz, is 12,715, or 6,458 CoreMark/core. That thrashes the Atmel device, which was tested to 21 MHz, where it netted 71 CoreMark.

Jack's addiction
There are some caveats. Some processors can load the entire test in cache. For those, it makes sense to use some of EEMBC's more comprehensive benchmarks. Wait states are a problem, so tests report where the code runs: if it's from flash it'll generally be slower than from RAM. The nearly-shocking news that the Core i5 is less than two times the score/MHz for a Cortex M4 neglects nifty features like floating point (the i5 has an insanely-fast FPU, which the benchmark's integer tests ignore).

Some companies couple CoreMark with EEMBC's EnergyBench to compute performance per mA, a number of increasing importance.

Best of all, the code is freely available at www.coremark.org.

I've turned into a crack-head, and my drug of choice is the CoreMark scores. It's fascinating to compare various processors and compilers. The results can be pretty surprising.

Thanks to Marcus Levy of EEMBC for answers to my questions.

Jack G. Ganssle is a lecturer and consultant on embedded development issues. He conducts seminars on embedded systems and helps companies with their embedded challenges, and works as an expert witness on embedded issues. Contact him at jack@ganssle.com. His website is www.ganssle.com.