Monday, May 14, 2012

Exynos Quad versus Tegra 3: Power efficiency

The Samsung Galaxy S III's quad core processor promises plenty of power. At the same time, the new Exynos chipset is built on Samsung's new 32 nanometer (nm) process and features dynamic voltage scaling.

The 32 nm should result in 20% power savings from older chipsets using a 45 nm process. Dynamic voltage scaling means that the quac core processor slows down and reduces power consumed when full power is not needed. Of course behind all this you have a large 2100 mAh battery.

Did Samsung deliver on its promise. GSM Arena has put the Galaxy S III through it battery life test, and studying the results is interesting.

The HTC One X has a Tegra 3 chipset, a quad core processor with a slow fifth companion core. In tasks requiring which do not require a lot of processing power the fifth core takes over and the powerful quad core processor goes to sleep. 

Talk time:
Galaxy S III: 10 hours and 20 minutes
One X : 9 hours and 57 minutes

We are pretty sure that for making GSM voice calls, the One X uses the single 500 MHz core. Given that the Galaxy S III has a much larger battery 2100 mAh battery than the One X's 1800 mAh battery, it would seem that the Tegra 3 beats the Exyos Quad in terms of power efficiency in voice calls.

Web browsing:
Galaxy S III: 5 hours and 17 minutes
One X: 4 hours and 18 minutes

The Galaxy S III has a Super AMOLED display, which saves a lot of power when displaying black images, but usually consumes a lot of power in web browsing tests since most web pages are white. Both phones have similar size displays (the Galaxy S III being fractionally larger), so we would expect that HTC One X to do better in this test.

This is where you see the advantage of dynamic voltage scaling. The Galaxy S III would not need the full power of its quad core processor to do web browsing, so in this test it would be running them at less than full speed.

The 500 MHz fifth core of the Tegra 3 on the One X won't be enough to do this task, so it switches to the quad core running at full speed. Basically, it is a low power or full power option, and despite the One X's LCD being more power efficient in this test, the processor consumes so much juice, that it negates this advantage.

If you look at other Super AMOLED equipped phones in this test, you will appreciate how much power voltage scaling on the quad core Exynos saves.

Galaxy S III: 5 hours and 17 minutes
Galaxy Note: 3 hours and 35 minutes
Galaxy Nexus: 3 hours and 1 minute 

Video playback:
Galaxy S III : 10 hours and 1 minute
One X : 5 hours and 45 minutes

Super AMOLED displays are efficient in video playback, so basically the result here is expected after looking at the web browsing tests.

Battery life benchmarks from GSM Arena: Source 1 and source 2.

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