AMD RyZen CPU Architecture for 2017

Discussion in 'PC Industry' started by fellix, Oct 20, 2014.

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  1. hoom

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    That looks like one of those minor quirks fixed with OS/BIOS tweak though?
    Not like the FPU is calculating wrong ...
     
  2. Clukos

    Clukos Bloodborne 2 when?
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  3. Kaarlisk

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    http://www.realworldtech.com/forum/?threadid=170454&curpostid=170458

     
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  4. Clukos

    Clukos Bloodborne 2 when?
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    Nice results for the R5s:

     
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  5. AlexV

    AlexV Heteroscedasticitate
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  6. Clukos

    Clukos Bloodborne 2 when?
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  7. 3dilettante

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    EPYC purportedly uses a B2 stepping, which might have a fix or general improvement in manufacturing that handled whatever is off about Ryzen under heavy utilization.
    I thought the last time it was discussed for Threadripper that it was using B1, which isn't different from Ryzen in general unless there's a minor revision number difference between affected B1 chips. However, didn't AMD state that the highest binning chips went into Threadripper? If there's something variable like timings or physical characterization in early chips, perhaps they flake out on chips that don't meet the highest bins or don't get the same level of power-delivery or overall platform quality that an X399 board would.

    Perhaps another reason might be that the multi-die setup of Threadripper and EPYC might be injecting a bit of latency somewhere that is slowing down some borderline portion of the memory pipeline due to extra synchronization or longer stalls.
     
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  8. Clukos

    Clukos Bloodborne 2 when?
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    It doesn't affect every Ryzen chip apparently, only some. So it could be something related to early samples perhaps.
     
  9. Malo

    Malo Yak Mechanicum
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    It indicates there definitely was a revision at some point though.
     
  10. 3dilettante

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    That would go to the question of whether there is a smaller increment to the steppings besides just B1 and B2.
    If the circuit revision is consistent between affected and unaffected chips, then it's not immediately clear that AMD has fixed something.
    If there were more sample data, it might be possible to see if there was a range of affected weeks, or if specific SKUs were more likely to be affected. The binning process might have been tightened after some point, which may explain why the less-forgiving high-end or high-reliability products don't see this within their factory clock ranges.

    There's no clear indication that this can be fixed by an update, which may mean something like the microcode can't work around a timing path hit by bad binning, or something else that it cannot readily change due to characterization data written or fused by an older evaluation suite. Even if the bad data is in microcode, without the necessary testing environment there may not be a way to set the correct values in the wild.
     
  11. Anarchist4000

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    That was my thinking as well as it seems to be an obscure timing issue with some event happening too quickly. Might actually be memory timings in conjunction with Infinity, as TR/Epyc have relatively low memory clocks and not widely tested yet.

    Doesn't occur on Windows, only Linux and only with some models according to the Phoronix article, so they might be able to fix it through software. Delaying the scheduler a couple cycles or whatever is required shouldn't be overly harmful to performance. Strange they haven't addressed it, but it could be in a future kernel update that hasn't been tested.
     
  12. 3dilettante

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    At least some of the descriptions of reported issue indicate this may not be limited to memory speeds above what EPYC officially supports.

    Without knowing the cause, we may not be able to rule out a difference in the way the platforms handle specific kernel functions or how and where they allocate resources. Hitting a TLB corner case or hitting kernel and user space addresses in a certain sequence can be unique to the OS architectures. However, it would be disruptive to change a kernel function or remap buffers for a few steppings.
    I am not sure which scheduler you are referencing in this case. OS thread scheduling in a high load case is probably not trying to intercede that frequently, and the internal scheduling of the SOC, CPU, or non-OS software routines may not be up to the kernel to modify.
     
  13. hoom

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  14. Clukos

    Clukos Bloodborne 2 when?
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    I've ran two tests with AoTS GPU/CPU with the 1700 at 3.8 GHz and my optimized 3466 timings:

    [​IMG]
    [​IMG]

    I've also ordered the Noctua U12s to replace my Wraith Spire, hopefully i'll be able to run the 1700 at 4.0GHz with that :D
     
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  15. Clukos

    Clukos Bloodborne 2 when?
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  16. Clukos

    Clukos Bloodborne 2 when?
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    Got the NH-U12s with the AM4 kit, looks quite nice :)

    [​IMG]

    Now I can get stable 4 GHz with 1.38 vcore, max temp doesn't exceed 70C during stress testing and it is dead silent!
     
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  17. fellix

    fellix Hey, You!
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    I have the same cooler for my i7-6800K rig. Naturally, it barely sweats @4GHz and 1.25V with much headroom left, but I like it quiet foremost. :p
     
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  18. Clukos

    Clukos Bloodborne 2 when?
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    Aida64 CPU benchmarks with the 1700 at 4.0 GHz:

    [​IMG][​IMG][​IMG][​IMG][​IMG]

    :)

    Edit: 7-zip if anyone is interested:

    [​IMG]
     
    #2478 Clukos, Aug 20, 2017
    Last edited: Aug 20, 2017
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  19. Kyyla

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    Noctua makes nice coolers. My previous one lasted me about 10 years.
     
  20. Kaotik

    Kaotik Drunk Member
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    Yes, but for the love of everything holy, they do not have any taste on colors they use.
     
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