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Testing Out The Configurable TDP On AMD's Kaveri

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  • Testing Out The Configurable TDP On AMD's Kaveri

    Phoronix: Testing Out The Configurable TDP On AMD's Kaveri

    AMD Kaveri APUs offer a configurable TDP to target running the APU at lower power rating and this feature can be configured on supported motherboards. While the configurable TDP is targeted for the lower-end Kaveri APUs, I ran some tests from the A10-7850K when bumping its TDP from 95 Watts to 45 to 65 Watts to see how the performance is impacted.

    http://www.phoronix.com/vr.php?view=19714

  • #2
    From the benchmarks, CPU performance seems to be much more constrained by the TDP than GPU. So either the GPU is extremelly efficient or it is bottlenecked by something else, which may very well be the CPU itself. Maybe overclocking the CPU will render further FPS gains in graphics benchmarks.

    Comment


    • #3
      And what about heat and power consumption? That's kind of the point of TDP...

      Comment


      • #4
        missing Power Consumption

        I agreee with GreatEmerald, the article does seem to be missing Power Consumption...maybe an update to the article later on?

        Comment


        • #5
          Interesting results, Kaveri really does good when paired with a low TDP.
          It's also showed by the A8-7600, which in most benchmarks is always just 10/15% slower than the A10-7850K, while having a lower TDP and a lower clock. (Too bad that AMD didn't send you one of those too, Tje A8 should be ~$70 cheaper than the A10 when it hit the market, so a comparision under Linux would have been interesting).

          It really shows that Kaveri was optimized to work with low TDP. Or maybe it's just because it's using 28nm SHP, who knows.


          It's also interesting to see the Watt per FPS performance (results rounded, I've assumed that auto is 95W):
          Xonotic
          45W - 2.95 W/fps
          50W - 2.8 W/fps
          55W - 2.63 W/fps
          60W - 2.43 W/fps
          65W - 2.3 W/fps
          95W - 1.71 W/fps

          x264
          45W - 1.53 W/fps
          50W - 1.48 W/fps
          55W - 1.4 W/fps
          60W - 1.31 W/fps
          65W - 1.26 W/fps
          95W - 0.97 W/fps

          Comment


          • #6
            Originally posted by Spittie View Post
            [...]
            Damn, fps/W, not W/fps.

            Comment


            • #7
              Originally posted by Spittie View Post
              It's also interesting to see the Watt per FPS performance (results rounded, I've assumed that auto is 95W)
              Very nice! So it seems that the further you drop the TDP the more efficient it becomes. That will surely bring some very interesting laptop CPUs.

              Comment


              • #8
                Originally posted by Spittie View Post
                It's also interesting to see the Watt per FPS performance (results rounded, I've assumed that auto is 95W):
                Xonotic
                45W - 2.95 W/fps
                50W - 2.8 W/fps
                55W - 2.63 W/fps
                60W - 2.43 W/fps
                65W - 2.3 W/fps
                95W - 1.71 W/fps

                x264
                45W - 1.53 W/fps
                50W - 1.48 W/fps
                55W - 1.4 W/fps
                60W - 1.31 W/fps
                65W - 1.26 W/fps
                95W - 0.97 W/fps
                Eh? How are you getting these numbers? Also, what is "W/fps" wouldn't efficiency be calculated in FPS/W (as in how many FPS you get per 1 watt → higher is better)?

                Comment


                • #9
                  Yeah, I think that is fps / watt. Though it shouldn't really be that surprising that doubling tdp doesn't double performance - we have known for years we have been descending this sliding scale of performance gains by just overvolting the same silicon. That is why the original p4 failed at 200w, Nehalem capped at 150w, and Ivy Bridge could barely push 120w without hitting huge volt limitations / diminishing returns.

                  Better silicon means more efficient processes, but that means you hit the roofs of performance at lower wattages.

                  Good to know Kaveri is rocking it at low tdp finally - the 28nm node seems to be doing good things for AMD. Intel might finally feel a sting in their sub-50w parts.

                  Comment


                  • #10
                    Originally posted by Figueiredo View Post
                    From the benchmarks, CPU performance seems to be much more constrained by the TDP than GPU. So either the GPU is extremelly efficient or it is bottlenecked by something else, which may very well be the CPU itself. Maybe overclocking the CPU will render further FPS gains in graphics benchmarks.
                    Yes, it's the RAM-bound GPU that makes the GPU look 'unaffected' from what I can tell. There was a discussion about this a couple weeks ago in another article which lead Michael to then go and do another article based on Kaveria (sorry, no link. I just use the RSS feeds) a couple days ago about this which pretty much backed up the theories (which was originally about how bound to RAM the onboard GPU's from even the early days actually were).

                    It's why I've always bought the highest compatible RAM for my HTPC's and low-end machines. No point burning power that's unused because the GPU was throttled. But now we can reduce the power usgae (with proof yet to come on ACTUAL power consumption) and still get damn fine GPU-based performance. Good times all-round I say, especially in light of games not really requiring much in the way CPU performance.

                    Comment


                    • #11
                      Originally posted by Spittie View Post
                      Interesting results, Kaveri really does good when paired with a low TDP.
                      It's also showed by the A8-7600, which in most benchmarks is always just 10/15% slower than the A10-7850K, while having a lower TDP and a lower clock. (Too bad that AMD didn't send you one of those too, Tje A8 should be ~$70 cheaper than the A10 when it hit the market, so a comparision under Linux would have been interesting).

                      It really shows that Kaveri was optimized to work with low TDP. Or maybe it's just because it's using 28nm SHP, who knows.


                      It's also interesting to see the Watt per FPS performance (results rounded, I've assumed that auto is 95W):
                      Xonotic
                      45W - 2.95 W/fps
                      50W - 2.8 W/fps
                      55W - 2.63 W/fps
                      60W - 2.43 W/fps
                      65W - 2.3 W/fps
                      95W - 1.71 W/fps

                      x264
                      45W - 1.53 W/fps
                      50W - 1.48 W/fps
                      55W - 1.4 W/fps
                      60W - 1.31 W/fps
                      65W - 1.26 W/fps
                      95W - 0.97 W/fps
                      You do realize that TDP is a measure of heat production not energy draw right? Hence it expanding to: Thermal Design Power...

                      Comment


                      • #12
                        This is one of the features I found really interesting. New, tech-stuffish and definitely interesting. While you won't enable it on raw compiling, video rendering or excessive gaming, you might throttle it down nicely for HTPCs, surf stations and so on. You could even buy them in 10 packs with a rebate and then put them in different boxes for different purposes. Just configure one to be your little HTPC with ASIC aided video decoding and one as you big boom machine for Gentoo compiling or similar things.

                        The mainboard looks also interesting though I'd rather go with the A88X-Plus cause it has 3 classic legacy old school PCI slots (for my bazillion of PCI cards I still have and use), as well as lots of SATA and USB headers.

                        Comment


                        • #13
                          Originally posted by Luke_Wolf View Post
                          You do realize that TDP is a measure of heat production not energy draw right? Hence it expanding to: Thermal Design Power...
                          You do realise that the laws of thermodynamics still applies? If it's producing 45W of heat, it's at least using 45W of electricity.

                          Comment


                          • #14
                            Cool! Thanks for the 45 W and 65 W TDP numbers! I assume they'd be in the same ballpark as the A8-7600.

                            As for TDP, it's my understanding that it is determined by measuring the average (or peak minus outlier spikes) power consumption during a particular type of prolonged stressful CPU load and case temperature. For Intel, their TDP measurements are done doing some "typical" software loads while AMD uses more stressful loads (ie. benchmarking software) so AMD TDPs and Intel TDPs can't exactly be compared directly. I guess with integrated GPUs they also add GPU loads.

                            Comment


                            • #15
                              Interesting things are afoot in AMD land.

                              The current model only implements two of the four possible memory controllers. So it looks like AMD has the intention to address the RAM bandwidth issue one way or another. The another being GDDR graphics RAM.

                              Originally posted by stiiixy View Post
                              Yes, it's the RAM-bound GPU that makes the GPU look 'unaffected' from what I can tell. There was a discussion about this a couple weeks ago in another article which lead Michael to then go and do another article based on Kaveria (sorry, no link. I just use the RSS feeds) a couple days ago about this which pretty much backed up the theories (which was originally about how bound to RAM the onboard GPU's from even the early days actually were).
                              This has always I been an issue with APUs. In fact it was an issue when GPUs wgphere integrated into external chip sets. Nothing beats bandwidth for a GPU.
                              It's why I've always bought the highest compatible RAM for my HTPC's and low-end machines. No point burning power that's unused because the GPU was throttled. But now we can reduce the power usgae (with proof yet to come on ACTUAL power consumption) and still get damn fine GPU-based performance. Good times all-round I say, especially in light of games not really requiring much in the way CPU performance.
                              This new APU of AMDs is a bigger leap forward than a lot of people want to admit to. Frankly these days there are many applications where the CPU not the most important element of the machine, it isn't just gaming.

                              Comment

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