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The ECC DDR4 RAM Overclocking Potential With AMD Threadripper On Linux

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  • schmidtbag
    replied
    Originally posted by ddriver View Post
    Overclocking doesn't imply pushing to the limit, merely above the stock clocks. It doesn't need to introduce instability. Crucal has ecc modules rated at 2400 and 2666 that are practically identical, the only thing that differs is the timings, and not surprising in the least, they all cost the same down to the cent. It is just two SKUs of the same hardware product, so overclocking the 2400 one to 2666 is something I doubt will result in the slightest increase in instability.
    You do know of binning, right? Not all silicon is equal. Typically (though probably not always) slower speeds exist because the hardware can't be pushed any harder. When you've got a product focused on stability, the constraints are much tighter.
    I agree going from 2400 to 2666 isn't going to have much (if any) impact on stability, but that's also not much of an overclock either.
    There is quite a margin for ddr4 to safely overclock as many chips are already capable of doing in excess of 4000, and the only reason ecc memory is still stuck at 2666 is jedec never bothered to update their specifications, which they didn't do not because it is unfeasible, but because it is something that they haven't deemed necessary for the time being.
    You say that as though 4000 is a standard for non-ECC, which as far as I'm concerned, it isn't according to JEDEC (2400 was the standard but I think it was increased to 3200). That being said, as far as I'm concerned, JEDEC can't be the reason why ECC is stuck at 2666, since non-ECC doesn't conform to their standards either.
    RAM manufacturers care about profits, which is why they go ahead and release "pre-overclocked" modules. So, the lack of ECC at 3Ghz+ is either because:
    A. There's some industry regulation I'm not aware of that legally prevents them from doing so.
    B. There's no demand (which is BS).
    C. Because they can't guarantee performance/reliability - something ECC users care about since that's the sole purpose of ECC.
    Anyway - I have no doubt ECC is capable of going higher. But can!=should. This is probably why neither AMD nor Intel offer overclocking on their server platforms.
    Power usage is also a concern, especially in high density datacenters, especially when using high capacity fb memory. Enterprise hardware, in general, aims for the optional power\performance ratio, which is also why even low core count server cpus are fairly underclocked, even if they have ample TDP budget to increase per-cpu performance.
    I agree with all of this.

    Originally posted by MaxToTheMax View Post
    I'm not exceeding spec on the actual RAM. If anything, ECC is advantageous for overclocking, because it'll warn you if your OC isn't stable, and may actually correct errors caused by a bad OC until you can ease it back.
    If you are overclocking, by definition, that is exceeding the specs. However, I would agree with your other point.

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  • hotaru
    replied
    Originally posted by ddriver View Post
    But for epyc, with its 8 channel MC, it is also kinda redundant as bandwidth is ample even at lower clocks.
    epyc does have plenty of memory bandwidth, but it can still benefit from the infinity fabric running at higher clock speeds.

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  • MaxToTheMax
    replied
    Originally posted by schmidtbag View Post
    In general, overclocking ECC is pretty counterproductive. The whole point of having ECC is to improve stability and reliability. When you overclock, you're going beyond the manufacturer's specs, therefore pushing beyond the intended limits of the product. So basically the benefit you're paying extra for is negated.
    Despite all of this though, I think it's great AMD at least gives users an option, and I also think DDR4 ECC is clocked way too low.
    I'm not exceeding spec on the actual RAM. If anything, ECC is advantageous for overclocking, because it'll warn you if your OC isn't stable, and may actually correct errors caused by a bad OC until you can ease it back.

    Leave a comment:


  • ddriver
    replied
    Originally posted by schmidtbag View Post
    When you overclock, you're going beyond the manufacturer's specs, therefore pushing beyond the intended limits of the product. So basically the benefit you're paying extra for is negated.
    Overclocking doesn't imply pushing to the limit, merely above the stock clocks. It doesn't need to introduce instability. Crucal has ecc modules rated at 2400 and 2666 that are practically identical, the only thing that differs is the timings, and not surprising in the least, they all cost the same down to the cent. It is just two SKUs of the same hardware product, so overclocking the 2400 one to 2666 is something I doubt will result in the slightest increase in instability.

    There is quite a margin for ddr4 to safely overclock as many chips are already capable of doing in excess of 4000, and the only reason ecc memory is still stuck at 2666 is jedec never bothered to update their specifications, which they didn't do not because it is unfeasible, but because it is something that they haven't deemed necessary for the time being.

    Power usage is also a concern, especially in high density datacenters, especially when using high capacity fb memory. Enterprise hardware, in general, aims for the optional power\performance ratio, which is also why even low core count server cpus are fairly underclocked, even if they have ample TDP budget to increase per-cpu performance.
    Last edited by ddriver; 23 December 2018, 08:40 PM.

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  • schmidtbag
    replied
    Originally posted by milkylainen View Post
    That's some seriously nice scaling!

    But I don't see why ECC should be a much harder overclock?
    It's a few bits more to store the ECC...
    Sure. Slightly more load and xtalk, but should be negligible if it's properly wired.
    Some latency added.. you might not reach ludicrous overclocks... but still respectable ones.
    In general, overclocking ECC is pretty counterproductive. The whole point of having ECC is to improve stability and reliability. When you overclock, you're going beyond the manufacturer's specs, therefore pushing beyond the intended limits of the product. So basically the benefit you're paying extra for is negated.
    Despite all of this though, I think it's great AMD at least gives users an option, and I also think DDR4 ECC is clocked way too low.

    Leave a comment:


  • ddriver
    replied
    AMD seems to be confident enough about zen 2 to even certify ddr 3200 ecc, provided of course jedec do their part and add that speed to the official specification. Otherwise it will cap at 2933 it seems. Sadly, AMD will probably once more only certify epyc and leave the consumer and prosumer workstation ecc support to the uncertainty and whims of motherboard vendors.

    There is nothing intrinsically obstructing the overclock of ecc ram, other than chip binning. I've tried a number of 2400 modules and most of them seem to be able to do 2933 with just some timing adjustment, and an eventual modest voltage boost. It is just that the chips that go into ecc memory don't have to be exceptionally good, so it is just market economics to blame that ecc modules can't match the speed for the fastest consumer memory.

    Another factor that prevents crazy clocks is that the industry generally doesn't care about memory corruption on consumer systems, wheras for the enterprise that is unacceptable, so clocking is a tad more conservative, as going overboard will just throw too much errors, and unlike a consumer system, those errors will show.

    At any rate, decent yield dram chips will have no problem enabling 3200 ecc modules. Although the incipient 32 gig udimm modules will hardly be able to hit those clocks. But for epyc, with its 8 channel MC, it is also kinda redundant as bandwidth is ample even at lower clocks.
    Last edited by ddriver; 23 December 2018, 07:12 PM.

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  • MaxToTheMax
    replied
    Originally posted by milkylainen View Post
    That's some seriously nice scaling!

    But I don't see why ECC should be a much harder overclock?
    It's a few bits more to store the ECC...
    Sure. Slightly more load and xtalk, but should be negligible if it's properly wired.
    Some latency added.. you might not reach ludicrous overclocks... but still respectable ones.
    Yeah, my findings are that it might not reach the same peak clocks, but getting decent clocks is trivially easy.

    Much of the scaling is probably due to the higher Infinity Fabric clocks. On Threadripper systems, it's probably worth putting up with crap timings just to get higher raw clocks, for that reason. Although I didn't test this.

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  • rene
    replied
    also still need to try EEC memory on my Mini-ITC Ryzen 2700 build, … https://www.youtube.com/watch?v=jZNvj67PAEc

    Leave a comment:


  • pegasus
    replied
    Key question is how does TR behave with two dimms per channel ... Epyc server boards we have claim that with 2dpc clock goes down to 2133. Haven't tried manually bumping it higher (yet) ...

    Also I see that numa + openmp is mistery to many people on the benchmarking scene, including phoronix test suite. I may be motivated to collect some nice material from the hpc sites and put together some text if Michael is willing to publish it. It's high time that wider world learns how to make best use of numa machines ...

    Leave a comment:


  • milkylainen
    replied
    That's some seriously nice scaling!

    But I don't see why ECC should be a much harder overclock?
    It's a few bits more to store the ECC...
    Sure. Slightly more load and xtalk, but should be negligible if it's properly wired.
    Some latency added.. you might not reach ludicrous overclocks... but still respectable ones.

    Leave a comment:

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