Samsung Galaxy S4 overclocks GPU to fudge benchmark results

Smartphones these days sell based solely on their merits and how powerful they are, and benchmarking is one of the few ways to find out how powerful a smartphone processor is. So what do you do if you’re a big name with a very successful brand and want more profit? Investing in R&D, marketing and good quality is one way out, but a shorter, much cheaper way to more money can be a bit of cheating.

The Samsung Galaxy S4 is a great phone and employs one of the best SoCs to date: the Exynos 5 Octa 5410. This SoC is based on ARM’s big.LITTLE architecture, and uses four low-power Cortex A7 cores clocked at 1.2GHz and four fast Cortex A15 cores clocked at 1.6GHz. The system alternates between the two quad-core processors depending on the load to deliver commendable performance and good battery life. A  PowerVR SGX 544MP3 handles the graphics.

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Now, the S4’s GPU is capable of running at up to 533MHz, but it is locked at a frequency of 480MHz for all applications and games. However, the guys at AnandTech have found that the S4 actually overclocks the GPU to 533MHz when running certain benchmarking applications, including GLBenchmark 2.5.1, AnTuTu and Quadrant. 

Fooling benchmarks to get the upper hand?

However, running the latest version of GLBenchmark (GFXBench 2.7.0) shows that the GPU is clocked at 480MHz. Tests show that the S4’s performance was almost 13.8 percent higher when running GLBenchmark 2.5.1 than on GFXBench 2.7.0 thanks to the GPU being boosted to the higher 533MHz frequency. The CPU performance is similarly boosted to the maximum frequency available when GLBenchmark 2.5.1, AnTuTu, Linpack, Benchmark Pi or Quadrant is launched. Again, running GFXBench 2.7.0 causes the SoC to switch to a low frequency.

Turns out, there’s an application that changes the Dynamic Voltage and Frequency Scaling (DVFS) behaviour of the SoC to scale up the GPU clock if a benchmark app is run. Quadrant’s standard, advance and professional variants; AnTuTu and Benchmark Pi are all mentioned in the application’s whitelist. It seems the application also listens for other benchmark applications not in the whitelist, as GLBenchmark wasn’t mentioned.

While all of this doesn’t really affect real world performance, it does mean that you should take benchmark results of the Exynos 5 Octa-powered Galaxy S4 variants with a large helping of salt. The 480MHz default clock isn’t all that far away from the full 533MHz frequency, and Samsung might have decided to stick with the lower clock to ensure stability. However, that doesn’t mean this isn’t cheating. We think Samsung should have focused more on improving the user experience than spending large amounts of time making an application for fooling benchmarks. 

For more details, read the entire report at  AnandTech.