Qualcomm’s flagship SoC is a departure from the company’s custom-core approach, because it relies on stock ARM cores, and because has eight cores in big.LITTLE rather than just four custom CPU cores. It is also the company’s first 20nm application processor. 

Great on paper, not so great in real life

The use of ARM reference cores was never expected to be much of a problem, and TSMC’s 20nm was already used for Apple and Samsung flagship SoCs.

However, somewhere along the line, Qualcomm’s design started experiencing thermal issues, causing a bit of a problem for the company. Ars Technica recently published the findings of a series of throttling tests carried out by Primate Labs, which show how serious the issue really is.

The Snapdragon 810 was pitted against its predecessors, the Snapdragon 801 and 805, and in both cases it exhibited a lot more throttling under sustained load.

2.0GHz part usually runs at a lot less

The tests demonstrate that 15 minutes of load force the Snapdragon 810 to throttle quite aggressively, but that wouldn’t be a huge problem if the chip managed to run at full speed for a few minutes.

Image via Ars Technica

However, the team found that the Snapdragon starts throttling just seconds into the test. The chip rarely comes near its top clock of 2.0GHz, and usually it takes just 45-90 seconds for the clock to dip to between 1000MHz and 1400MHz. What’s more, a few minutes into the test, the chip starts switching to smaller Cortex-A53 cores, which are usually capable of running at 1.5GHz, giving the user the impression that the whole chip is running at said clock.

However, by the time the small cores kick in, roughly halfway through the test, the Cortex-A57 cores experience severe throttling and settle down south of 1000MHz. While all flagship SoCs exhibit some measure of throttling, the team pitted the 810 against Samsung's Exynos 7420 and the results speak for themselves. In sustained performance, it's no contest.