Threadripper 1950x RAM Benchmarks - Frequency vs Timing

Discussion in 'AMD Processors' started by dpow7, Feb 12, 2018.

  1. dpow7

    dpow7 n00bie

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    I've tried looking for benchmarks comparing RAM frequency with CPU performance for the Threadripper 1950X, but I can't seem to find what I'm looking for. I'm looking to install 8gb in Quad Channel (32gb total) of 1Rx8 SS RAM.

    I know that the Threadripper performance increases with RAM frequency due to the design of the infinity fabric, so all the benchmarks show increased performance as RAM frequency increases.

    However, I can't seem to find benchmarks for increased frequency at decreased timings. Specifically, I'm looking for 3200 @ 14 vs 3600 @ 18.

    On paper, the 3200 @ 14 is faster ram (8.75ns) vs the 3600 @ 18 (10ns); but the infinity fabric seems to love RAM frequency increases. Thus, I'm not sure which RAM to buy. I've checked the VQL and both are listed at compatible at those speeds, so I'm assuming I should get the rated speeds on each. Any input (or preferably links to benchmarks) from you guys on which route to go? Cost difference between the two is $1, so I'm now only concerned with performance.
     
  2. Speedeu4ia

    Speedeu4ia Limp Gawd

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    Only thing I would say is 3200 cl14 will OC well anyway and wouldn't pay more
     
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  3. Aluminum

    Aluminum Limp Gawd

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    2DPC on TR is somewhat dicey at higher speeds, even SRank dimms. 1DPC DRank dimms (with twice the capacity) are apparently easier to run fast.
     
  4. Neapolitan6th

    Neapolitan6th Limp Gawd

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    I second this. I only have X99 experience here, but it is honestly just as bad as ryzen in terms of memory support.

    I have a 2133 kit and was able to push it to 3200 cl15 (would post at 3400 even)

    I would say get the cl14 3200 kit and with some tweaking you could hopefully get it to 3600 by loosening the timings. No guarentee with ryzen getting ddr4 that high though. Sometimes they post, but performance actually goes down.
     
  5. dpow7

    dpow7 n00bie

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    I've checked the VQL so I know I can get those speeds with the RAM I want to buy. I'm just not sure about overall performance at faster frequency and slower timings.

    You're suggesting changing to a 16gbx2 configuration. I thought that would slow performance (assuming same frequency and timings) due to a dual channel configuration instead of a quad channel configuration. Am I mistaken on that?
     
  6. Aluminum

    Aluminum Limp Gawd

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    No, 4 slot vs 8 slot. DPC = dimm per channel (all server tech docs I've seen use this nomenclature) and going 2DPC on TR (4 channels) means 8 dimms which is often troublesome and very hard to get fast, QVL or not. 8x8 SR on TR is hard, 4x16 DR not as hard, 8x16 DR good luck. All current 16s are DR, 8s can be SR or DR. On amd you want b-die period, other stuff can work but look at the bios time gap on am4 ryzen as an example.

    I'm saying that the 4x8GB SR (if they really are SR, but 3200C14 should be b-die which is) is the best bet to clock high. Not sure what 3600C18 is but I would pass on it, 3600 is barely heard of (esp "proven") on TR and going to be cpu/board/bios lottery even on b-die.
     
  7. Aluminum

    Aluminum Limp Gawd

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    Keep in mind QVLs are not a guarantee either, nowhere near as much as the motherboard and ram vendors try to imply.
     
  8. dpow7

    dpow7 n00bie

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    The 3600c18 is SR b-die also according to some posts I've seen on reddit. Ignore the different models and just look at the timing for a second. Let's say I'm able to get the same b-die set to run at 3600c18 and 3200c14. How much does the infinity fabric benefits at higher frequency?

    3600 @ 18 has a true latency of 10ns
    3200 @ 14 has a true latency of 8.75ns

    So, the 3200 is actually the quicker RAM configuration. However, I'm unclear how much the infinity fabric benefit at 3600 vs 3200. At which speed would you theoretically expect better overall system performance?
     
    Last edited: Feb 18, 2018 at 4:26 PM
  9. sirmonkey1985

    sirmonkey1985 [H]ard|DCer of the Month - July 2010

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    After 3200 mhz the gains are very minimal in real world applications. I'd go with 3200 cl14.