For months, rumors have dogged Qualcomm that its Snapdragon 810 SoC ran hot, and that these issues were behind Samsung’s decision to adopt its own 14nm technology for the Samsung Galaxy S6. Other sources indicated this was essentially a foundry move. Samsung needed to keep its fab full after Apple decided to move production back to TSMC for the A9, and the company could in-house its own designs on its up-and-coming 14nm — so why not go for it? A new investigation backs up the heat problems and demonstrates that the Qualcomm 810 does have thermal issues that other devices haven’t experienced.

Ars Technica put the Snapdragon 810 (in the LG G Flex 2 and the HTC M9) to the test and compared it against other devices using the Snapdragon 801 and 805 silicon. These were chips built on the more mature 28nm process, with lower theoretical peak performance using the stress test in Geekbench. That test has recently been revised to capture real-world scenarios more accurately — these results don’t just slam every core to maximum workload and call it done.

The results aren’t kind to Qualcomm’s 810. And the comparison against Samsung’s Exynos 7420, the 14nm chip in the Galaxy S6, is particularly ugly:

Both chips throttle (as does every other chip that Ars tested), but the Snapdragon 810 throttles much more heavily. The missing dashes in both lines represent the times when both cores shifted over to their “Little” cores. Doing so allowed the Snapdragon 810 to briefly increase its clock speed, but every time the big cores engaged, the chip had to downthrottle to keep from overheating.

So, does the Snapdragon 810 have a thermal problem? Insomuch as the chip throttles more than its predecessors, and that throttling has a negative and noticeable impact on the device, yes. But that’s not the end of the story.

Reap what you sow

There’s no arguing that Samsung’s Galaxy S6 comes out a winner compared with Qualcomm’s 810 in the comparison above, as do the older 28nm chips. It’s only fair, however, to note that part of the reason these problems exist is because manufacturers have relentlessly focused on slicing away at the thickness and weight of their devices. The first Samsung Galaxy S phone was between 9.9mm and 14mm thick depending on the sub-type you purchased. It used a single-core Cortex-A8 CPU built on a 45nm process node and clocked at 1GHz. The modern Samsung Galaxy S6 uses an eight-core Cortex-A57 / 53 CPU, and despite the changes to the Geekbench test, that chip doesn’t sit anywhere near its claimed 2.1GHz. Instead, the chip hits an average clock of around 1.6GHz.

This problem isn’t unique to the smartphone or tablet market. Intel’s Core M has similar issues in certain configurations and for the same reason: OEMs are building devices that don’t actually take their SoCs operating requirements into full account. To some extent, this is intentional — Intel has told us that when it designed Core M, it gave OEMs more flexibility to choose their own thermal operating margins and clock envelopes — but when it crosses the line into selling devices that don’t have enough cooling to deliver the same experience their predecessors did, that’s an issue.

The bottom line is this: Moore’s Law no longer scales the way it did for any device, ARM or x86. The insistence on slashing both thickness and weight while simultaneously amping up core counts means that device manufacturers have a narrow path to walk. It’s fair to say that Qualcomm’s chip has disadvantageous power characteristics, but some of the blame for the end result of that fact — a poor user experience — lies on the backs of companies like HTC and LG that chose to ship a hot-running chip in chassis that couldn’t keep it adequately cooled, rather than risking adding a millimeter of additional thickness or a better heatpipe.

It’s time to let go of the fantasy that one day Apple or Samsung will build a smartphone so thin it’s actually two-dimensional, and return to an era when devices were robust enough that they didn’t need bulky secondary cases that destroy their profiles anyway. Since doing so also allows for better cooling, and would give us better device performance in the long run, there’s really no downside here.