I think virtual reality (VR) will find a location next to the movie theater and TV set someday; but when I end the use of a round and take the phone out of the headset, I still can’t help but notice the phone. Hot problem.
In order to understand the problem from the chip side, I further inquired about the graphics processing technology expert that Google encountered when it published Daydream, Qualcomm's vice president of graphics and imaging department TIm Leland; he said: "VR is what we encountered in the mobile phone The heaviest heterogeneous workloads -- a lot of work, much more than standard applications."
Specifically, VR requires a high data update rate for each new content of the frame, and also needs to calculate data from multiple sensors and respond with updated visual effects within 18ms to keep up with the user's head movements. .
In order to achieve the above goals, mobile phones need AMOLED displays that can be quickly switched to operate at near-high brightness without interruption; this task requires all components in the smartphone to wake up from sleep, including CPU, GPU, DSP, sensor hub core, display engine. And the video decoding function block, etc. are all close to full speed operation.
Of course, smartphones can support multitasking, but Leland said: "At that time, you have to keep the Wi-Fi function turned on, let the phone answer the phone, almost all functions are working; DRAM is also in operation, maybe Not fully powered, but at least in medium and high-end power modes."
Qualcomm is committed to maintaining the total power consumption of their chipsets and associated DRAM and power management IC chips within 5W; handset manufacturers can set the frequency and voltage settings, heat sinks, and board layers based on their choice. The number and the casing materials have autonomy in making the phone hot.
Leland pointed out that in Qualcomm's reference design, the default value is to keep the phone temperature below 35 °C, but mobile phone manufacturers can also set their own thresholds; in this regard, some manufacturers in the CPU governor set Set to be more radical, it will make the phone temperature reach 45 °C or above: "It feels like it will be very hot, but in fact it will vary according to the different materials of the phone case - each plastic has different heat resistance characteristics."
I didn't measure the temperature of the Pixel XL phone after using Daydream. Although I didn't feel the risk of burning it, I still noticed that the phone's hotness is unprecedented; it reminds me that some laptops can still be used. Used as an electric heater.
I am afraid that this situation will accompany us for a while. The most amazing VR headsets are currently tied to a PC with the highest-speed GPU and a wall-mountable power outlet; Intel and other vendors are designing that they don’t need to be paired with a computer to provide more The version of the user experience.
Leland believes that VR is only taking the first step in its 30-year development blueprint; AR technology that combines real and virtual worlds will include VR, which will become an AR one day. Mode.
And he also revealed that the next generation of Snapdragon will develop toward this trend, support the new Adreno GPU core, improve memory access efficiency and make full use of compressed data; in addition, the power management algorithm in the chip will also Take a more granular action, and in the video and display blocks will support the new feature of variable update rate: "So you don't have to change the display when you don't need it."
As for the total power consumption of 5W, there will not be much change, but Qualcomm will try to add more features. “Some software developers want to add photorealism to their applications, so they will limit the limits;†Leland said: “They want to add more visual processing to the security range, so I don’t know if the phone’s temperature can Drop a lot."
When I asked if the recent Galaxy Note 7 explosion would bring some obstacles, Leland's answer was that Samsung has the best team of engineers in the world, and there are also many innovations. The AMOLED display is also in a certain The degree of risk and the bet was born, but now the technology has spawned action VR devices: "Every leader will try to go beyond the limits, and every once in a while we will find where the limits are."
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