5 Replies
      Latest reply on Apr 9, 2017 7:03 PM by NotMyName
      3DTOPO Level 1 Level 1 (0 points)

        I am rendering the same amount of particles (using OpenGL ES) on the iPad 12.7" (with the original A9 chipset) as I am rendering on the iPhone 7 Plus (essentially indentical code).

         

        But, even though both A10 CPU and GPU is purported to be faster than the A9, to my surprise, the A10 CPU is working much harder compared to the iPad's A9.

         

        If I look at the Energy usage on the iPad Pro in Xcode, most the time it is at Low. While most of the time on the iPhone 7 plus it is Very High (sometimes it is even pegged out). That of course is a huge difference in power efficiency. I was expecting that the iPhone 7 Plus would have to work slighly less hard than the iPad Pro, not much much harder.

         

        I would like to understand why, and would very much appreciate any insight into this behavior.

        • Re: iPad A9 vs iPhone A10 chipsets
          KMT Level 9 Level 9 (14,505 points)

          Don't assume your code/APIs are optimized equally for both chipsets, chassied flash ram, etc.

            • Re: iPad A9 vs iPhone A10 chipsets
              3DTOPO Level 1 Level 1 (0 points)

              Everything is in memory, so I don't think the flash has any factor in play.

               

              But supposedly the A10 is 40% faster than the A9, its just hard to believe that it would actually be slower than the A9. If the optimization is that much worse for the A10, what is the point of claiming it is much faster than the A9?

               

              That said, after further optimizing the CPU usage, Instruments shows both devices using around 25% of Total CPU Usage (and in-fact all the statistics look quite similar for the two devices in the Energy Log Instrument) while in XCode it still shows the iPad as low energy impact and the iPhone as very high energy impact.

                • Re: iPad A9 vs iPhone A10 chipsets
                  KMT Level 9 Level 9 (14,505 points)

                       >and in-fact all the statistics look quite similar for the two devices in the Energy Log Instrument

                   

                  Yes, this might be more about Xcode's ability to form an accurate opinion than it is about device hardware.

                    • Re: iPad A9 vs iPhone A10 chipsets
                      3DTOPO Level 1 Level 1 (0 points)

                      Perhaps, but according to Instruments, they are performing about equally; the A10 is certainly not performing 40% faster or anywhere near that.

                        • Re: iPad A9 vs iPhone A10 chipsets
                          NotMyName Level 4 Level 4 (865 points)

                          The A10 showing a higher power consumption than the A9 may be the correct readings.  To quote from a tech article, since URL links cause problems:

                           

                          Benchmarking has revealed a mixed bag for A10 Fusion GPU’s performance, according to the analyst firm. Some benchmarks supported Apple’s GPU performance gain claims, and others fell way off. But the high levels of GPU performance are only temporary.

                           

                          The big problem is Apple’s GPU can’t sustain its peak performance for long without concerns of overheating, Linley Gwennap, founder and principal analyst at Linley Group, said in a research note this week.

                           

                          Apple has been amassing in-house graphics experts to improve the GPU technology in mobile devices. Apple made tweaks in the PowerVR GT7600 GPU architecture—which it licensed from Imagination Technologies—to improve performance.

                           

                          Gwennap estimates Apple increased clock speed by 50 percent to get those performance gains. The custom Apple GPU blows away competitors when operating at peak speed, but it can’t sustain that performance.

                           

                          “We believe the iPhone 7, to avoid overheating, throttles back from its top GPU speed after a minute or less, preventing it from achieving a high score for all users,” Gwennap said.