Infinity fabric clock uplift would make DDR4-4000 possible for Zen 3

Discussion in 'Frontpage news' started by Hilbert Hagedoorn, Oct 16, 2020.

  1. Hilbert Hagedoorn

    Hilbert Hagedoorn Don Vito Corleone Staff Member

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  2. Undying

    Undying Ancient Guru

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    I knew we gonna need a new ram kit with zen3, 3200 is not gonna cut it. 4000mhz cl19 costs 290Eur here atm which isnt that bad.
     
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  3. Uroshi

    Uroshi New Member

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    I thought the memory controller was exactly the same as in the 3000 series. Same IO die. Were the chiplets the ones limiting the clock rate?
     
  4. wavetrex

    wavetrex Maha Guru

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    IF sits between the IO die and CCDs.

    I/O die was already capable of much faster memory speeds, plenty of overclockers went beyond DDR4-5000 (2500Mhz) ... however, that was done with 2:1 ratio (memory:IF), because IF on Zen2 doesn't scale beyond 1900 Mhz, that's about the max.

    If the new CCDs have a better structure (for example, with the IF portion on the side instead of in the center, the IF links themselves may be a few millimetres shorter), allowing for that little bit of extra speed.

    Zen 2 ( all the I/O is smack in the middle, with cores on the sides)
    [​IMG]

    The IF had to travel from the middle UNDER half of the cache, and then converge on the I/O die:
    [​IMG]


    Zen 3 ( I/O is on one of the sides, most likely towards the I/O die )
    The length of the links themselves is most likely reduced by 30-40% !!

    And by the way his picture looks, there's a big-ass wide crossbar right in the middle of the die, that seems a very VERY wide bus !
    (Probably also how they managed to improve power efficiency, the X-bar is (much) wider and lower clocked, so consumes less power)

    [​IMG]

    Final edit:
    It will be interesting to see how this is arranged on the EPYC / Threadripper, with the asymmetrical CCD ...

    With Zen 2 EPYC, the CCDs could sit right near each other, as the IF were coming down from the middle:
    [​IMG]

    1, 2 __ 5, 6
    ==>[#]<==
    3, 4 __ 7, 8

    But with the new layout, that will not be possible anymore... so new EPYC will clearly look a bit different than current one !
     
    Last edited: Oct 16, 2020
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  5. nizzen

    nizzen Maha Guru

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    If you have 3200c14 b-die, they will pretty much overclock to whatever zen 3 can do with 1:1 infinity fabric :)
     
  6. Undying

    Undying Ancient Guru

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    Nah its a cl16 c die i think, gskill aegis is crap. I'll need a new kit. There is plenty of b die 3600 for cheaper so maybe get that one and overclock it.
     
  7. wavetrex

    wavetrex Maha Guru

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    Don't bother...
    The actual performance difference between 3200 and 3800-4000 will probably be small, and only show up in some edge cases.

    Especially considering the massive amount of cache, ALL addressable by every single thread (including that pesky "primary thread" of games), memory speed will probably play an even less role in Zen 3 than it did in Zen 2 (unless you choke it hard with 2133-2400 JEDEC speed or something like that)
     
    Last edited: Oct 16, 2020
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  8. Lily GFX

    Lily GFX Member

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    I think the silicon lottery will still be a thing thou on how high it is able run 1:1.
    I have one 3900X on my MSI X570 Godlike that is not able to run 3800 Memory and 1900 IF at all but runs
    3733 Memory CL16 and 1867 IF very stable with no odd swings in Memory speed and latency.

    I also have one 3800X in a different PC on a ASUS X570 Crosshair VIII Formula that is able to run 3800 Memory
    and 1900IF, but it had some odd swings in Memory speed and latency. So I adjusted that one too down to
    3733 Memory CL16 and 1867 IF and the odd swings in Memory speed and latency stopped.

    I did try to swap both CPU and Memory but result was the same, they both currently use same Memory settings.
     
  9. BReal85

    BReal85 Master Guru

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    I don't understand you. Graphs were showcased by using 3200 MHz RAMs as far as I remember. Or was this irony and I just couldn't detect it? :D
     
  10. Cidious

    Cidious Member Guru

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    I have 3 sets of Edie 32GB (2x16) 3200 CL16.. THEY ALL DO 4600 with reasonable voltages and timings. The only difference in binning between the kits is the tRFC which doesn't result in huge performance differences. Then I have 1 kit of Bdie 3200CL14 from Gskill. I can tell you the Edie costs half and delivers the same.. ALL edie kits can go above 4000. Most even up to 5000. (look for buildzoid on Youtube...) Don't waste your money on expensive bdie.. it's not worth it.. I've benchmarked the kits against each other at max 1900/3800 and tightest timings. MINIMAL margin in unnoticeable performance. Not worth spending double the money for!

    https://www.reddit.com/r/Amd/comments/eyoff9/please_stop_mindlessly_advising_people_to_buy/ my thread is still viable today. Please have a read.

    Please don't buy into the marketing! Don't waste your cash...
     
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  11. bluedevil

    bluedevil Master Guru

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    Seeing how ram speeds go up and up I wonder if gddr could be a good replacement for ram on pc like it's done on consoles. Market it for gamers and it will overthrow ram in a very short time.
     
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  12. wavetrex

    wavetrex Maha Guru

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    DDR5 will be pretty much as fast as GDDR5 was initially when introduced with Radeon HD 4000.

    However, the bus width is much smaller with DDR ( 128-bit for dual-channel ) than GDDR is on videocards, where the norm is 256-bit or more.
    So, even with the same clock speed, DDR transfer less.

    ... but, as HEDT CPUs like Skylake X or Threadripper have shown, memory bandwidth is not relevant for anything gaming, with "mainstream" dual-channel chips gaming the same or even better than HEDT.
     
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  13. Jawnys

    Jawnys Member Guru

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    I have a ddie kit on my intel 7700k from gskill 3200mhz and ive been pusing it to 3733 at cl 17 for five years so im sure that edie kit can do well on ryzen system for sure, i do have a bdie kit on my 3900x and run it at 3733 cl16 without issue
     
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  14. asturur

    asturur Master Guru

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    I'm pretty much happy to swap the cpu from 2700x to any 5x00x, and see how much i get for the simple cpu boost.
    And then tweak my 3200cl14 to whatever makes sense.
     
  15. geogan

    geogan Master Guru

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    I have 32GB of B-die 4000MHz kit, and I only run it at 3400CL14 all the time. It would never go much higher than that... never was stable at the max IF speed. Maybe it will go to full 4000CL16 on the 5900X, maybe not. But as said... the memory speed is not that critical these days given that most important time consuming code loops will usually fit in cache, a few cache misses to access main RAM will not slow it down too much.
     

  16. nosirrahx

    nosirrahx Master Guru

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    Lots of speculation going on here, it will be interesting to see what the benchmarks show because 3200 VS 4000 certainly will be requested a LOT.

    The only surprising performance differences I have seen is when overclockers have combined high frequency with hand tuned timings (primary, secondary and tertiary).
     
  17. Fender178

    Fender178 Ancient Guru

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    I am also interested in how this plays out because of watching Buildziod's take on the 5000 series CPUs. There was hoping that there would be some kind of improvement with Fclock. I also heard from Buildzoid's video on the 5000 series CPUs that the FClock isn't going to matter as much as it did with the 3000 series due to the fact the chiplets have access to all of the L3 cache at once instead of accessing it from 2 different pools.
     
  18. theoneofgod

    theoneofgod Ancient Guru

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    Still really curious to see memory latency. High 60 low 70 ns latency is not uncommon even for 3800 CL16A. I do hope to get reduced latency you just need Zen 3 and not buy faster RAM to technically brute force lower latency. My ancient i7 has lower latency on DDR3.
    You could say that it doesn't matter all that much, I still care about it.
     
  19. devastator

    devastator Member Guru

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    videocardz say zen3 overclock to 6 ghz may be fake though
     
  20. schmidtbag

    schmidtbag Ancient Guru

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    I don't think it's going to be all that necessary. Only Zen1 and Zen+ seemed to be especially hungry for memory bandwidth, but Zen2 overall fixed that problem. Even before Zen2, 3400MHz was pretty much the point of diminishing returns (or 3600MHz if you could find it on sale and keep it stable).

    Honestly, I think where AMD's better numbers are coming from largely has to do with better silicon. The 3950X for example was technically capable of reaching its advertised boost speeds, but realistically it didn't do that. When it was able to reach those speeds, it was only for brief moments, so effectively the boost clocks were lower. AMD got some flak for "false advertising" (I don't think it is false but it was shamefully misleading) and TSMC has improved their node, so I'm sure the boost clocks of these next-gen parts are more realistic, and running 1:1 will be easier.

    The speculation is pretty reasonable. We know what Zen2 can do, we know what its weaknesses are, and we know how Zen3 attempts to address them. That being said, I don't think there's going to be a compelling reason to spend extra and get 4000MHz memory, but I do think it'd be very interesting to see.
     
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