As pointed out in that Raspberry Pi 3 benchmarking article yesterday and has been pointed out elsewhere, this quad-core Cortex-A53 ARM development board does get rather warm under load. However, there is no heatsink at all by default with the RPi3.
After the big comparison results were finished up yesterday, I was monitoring the SoC temperature while running some more benchmarks on this $35 ARM board with Raspbian.
With the Phoronix Test Suite, it was simply a matter of setting MONITOR=sys.temp as an environment variable prior to using our open-source benchmarking software for enabling the thermal monitoring recording, which is polled concurrently while benchmarking and in the case of the Raspberry Pi 3 is exposed over sysfs via the Broadcom thermal driver for this SoC.
The few thermal images of the Raspberry Pi 3 were captured via the Seek Thermal that turns any Android phone or tablet into a low-cost thermal imager.
While running many benchmarks, the minimum SoC temperature was 39°C with a peak of 82.6°C and an average SoC temperature of 61.1°C. It's warmer than the Raspberry Pi 2 and I will get some side-by-side thermal comparison results shortly.
If you want to dig through this initial thermal data in more detail, visit this page on OpenBenchmarking.org. Stay tuned for more and if you didn't yet read yesterday's article, see Raspberry Pi 3 Benchmarks vs. Eight Other ARM Linux Boards.