Interesting. I have an old HTC phone running BOINC android with benchmarked 798.32 million ops/sec. It has a dual core ARMv7 processor that I limit to 60 C. I have experimented with other devices such as an octocore tablet, PC, laptop, etc. I have found that the more powerful devices get throttled back as the chips heat up (I don't use active cooling). If you have an old phone laying around, try running BOINC on it. I think power and cost-wise, you will be pleasantly surprised. In other words, I bet 20x $5 android phones running CPU Boinc tasks will beat the best $100 single board computer.