Thermal throttling with GearVR

Hi,

I've noticed that when running on a Samsung Note 4, the gpu is throttling down when the temperature rises, say, to 30C, and will throttle down from 500 to 266. Is this to be expected?

I tried fixing the gpu clock with OVRModeParm, but it still throttles down. I'm using Unity 5.0.1 and the Oculus Mobile SDK 0.5.1.

Here is the output from LogCat

I/VrApi (26282): CPU4 Clock 700 MHz, GPU Clock 266 MHz, Power Level State 0: normal, Temp 31.600000C

Any ideas?

Thanks
Tony

 

That's a normal behaviour. Here's some copy&paste from the Mobile SDK documentation:

Power management is a crucial consideration for mobile VR development.

A current-generation mobile device is amazingly powerful for something that you can stick in your pocket - you
can reasonably expect to find four 2.6 Ghz CPU cores and a 600 MHz GPU. Fully utilized, they can actually
deliver more performance than an XBOX 360 or PS3 in some cases.

A governor process on the device monitors an internal temperature sensor and tries to take corrective action
when the temperature rises above certain levels to prevent malfunctioning or scalding surface temperatures.
This corrective action consists of lowering clock rates.

If you run hard into the limiter, the temperature will continue climbing even as clock rates are lowered, and
CPU clocks may drop all the way down to 300 MHz. The device may even panic under extreme conditions. VR
performance will catastrophically drop along the way.

The default clock rate for VR applications is 1.8 GHz on two cores, and 389 MHz on the GPU. If you consistently
use most of this, you will eventually run into the thermal governor, even if you have no problem at first. A typical
manifestation is poor app performance after ten minutes of good play. If you filter logcat output for "thermal"
you will see various notifications of sensor readings and actions being taken.