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DDR4 Memory Speed Tests With The Core i7 6800K On Ubuntu Linux

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  • DDR4 Memory Speed Tests With The Core i7 6800K On Ubuntu Linux

    Phoronix: DDR4 Memory Speed Tests With The Core i7 6800K On Ubuntu Linux

    A few days ago I posted my first Core i7 6800K benchmarks under Ubuntu Linux compared to various other CPUs. Out of requests from some premium members, here are some straight-forward memory clocking tests of the i7-6800K on Ubuntu 16.04 LTS with the Linux 4.8 kernel. Tests were done from dual-channel DDR4 up through quad-channel DDR4 at DDR4-3000MHz.

    http://www.phoronix.com/vr.php?view=23566

  • #2
    Did the timings change when messing with the clock speeds? Some of these results don't really make sense.

    I'd also be interested to see results of real-world tests. Synthetic memory benchmarks are designed to take advantage of multiple channels.

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    • #3
      Originally posted by schmidtbag View Post
      Did the timings change when messing with the clock speeds? Some of these results don't really make sense.

      I'd also be interested to see results of real-world tests. Synthetic memory benchmarks are designed to take advantage of multiple channels.
      Results seem legit: the memory controller support DDR4-2400 (see here), that's why there isn't performance gap after 2400MHz.

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      • #4
        Err wait a minute... ii-6800K ark page says it supports DDR4 2400/2133 memory. Are you telling me that page is inaccurate and said CPU runs up to DDR4 3000 MHZ?

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        • #5
          Interesting benchmark! I would have liked a single channel benchmark as well though.
          I am thinking of making a low power (NAS) build with a Skylake Mini-ITX board and could probably save a bit of power by going single channel. However, I have yet to see a benchmark quantifying the performance difference.

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          • #6
            Originally posted by schmidtbag View Post
            I'd also be interested to see results of real-world tests. Synthetic memory benchmarks are designed to take advantage of multiple channels.
            x2, synthetics are a curiosity, but real world application performance is more meaningful. I suspect the difference is far more subtle in real usage, as was the case with DDR3.

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            • #7
              Originally posted by torsionbar28 View Post
              x2, synthetics are a curiosity, but real world application performance is more meaningful. I suspect the difference is far more subtle in real usage, as was the case with DDR3.
              Many other websites made this kind of tests. Results are all the same : in real world applications, the difference is close to 0 (generally <1%).
              Only some benchmarks and a few memory stressing programs can show something.

              Difference between DDR3 and DDR4, timings etc. show no difference too. I was so puzzled that I tried myself and... < 1% in all cases!

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              • #8
                I agree with schmidtbag, it would be interesting to see you do a similar test with a selection of perhaps 4 of these setups with real games (and some compilations?)! All of them probably aren't needed, since we only need to see if there is a correlation between the synthetic tests and a real-world scenario.

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                • #9
                  I've always wondered what the speed up from dual to quad channel was, but never went looking for benchmark results. I found the article interesting. Maybe others already knew these results, but I didn't.

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                  • #10
                    Originally posted by Passso View Post
                    Many other websites made this kind of tests. Results are all the same : in real world applications, the difference is close to 0 (generally <1%).
                    That's highly dependent on the workload. For some workloads (mostly threaded, data-dependent), memory bandwidth matters a great deal. For others, it's as you say.

                    Originally posted by Azpegath View Post
                    perhaps 4 of these setups with real games (and some compilations?)!
                    Unless you're using an iGPU (which this particular CPU lacks), games generally aren't a good way to stress main memory bandwidth.

                    Deep learning tends to be memory-bottlenecked (on GPUs, at least).

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