The primary benchmark being used for this benchmark is the MPI version of the NAS Parallel Benchmarks (NPB) from NASA. This test profile was used since NPB is quite popular for parallel computing, the tests are very reliable, there are a plethora of others using the NAS Parallel Benchmarks, and all-around are just really good Fortran-based benchmarks for testing multiple computing cores.
To look at how well the mini ARM cluster is scaling, there are benchmarks for the main NAS Parallel Benchmarks when using 1, 2, 4, 6, 8, 10, and 12 cores.
First up is the EP.B test, which is NASA's "Embarrassingly Parallel" benchmark with the class B problem size. When at one core of the PandaBoard ES the EP.B test is running at 5.27 Mop/s and then both cores on a single PandaBoard ES is at 10.3 Mop/s (+95%), at two PandaBoard ES nodes it's 19.26 (+86%), etc. When all six PandaBoard ES nodes are utilized, EP.B is running at 55.2 Mop/s, which is at 10.47x the speed of utilizing a single Cortex-A9 1.2GHz core on the OMAP4460 SoC. The scaling is actually better than was originally anticipated for using 10/100 Ethernet and a shared NFS mount from an SDHC card.