AMD Vega Hardware Reviews

Discussion in 'Architecture and Products' started by ArkeoTP, Jun 30, 2017.

  1. ToTTenTranz

    Legend Veteran Subscriber

    Joined:
    Jul 7, 2008
    Messages:
    9,839
    Likes Received:
    4,456
    Yes, not to mention these are review units where the Vega 56 cards may even be artificially salvaged chips (i.e. Vega 64 GPUs with a Vega 56 bios).
    The Vega 56 are not only coming later but also being packaged in a different facility.

    Results for undervolt + overclock are a lottery anyways.
     
    Lightman and Grall like this.
  2. seahawk

    Regular

    Joined:
    May 18, 2004
    Messages:
    511
    Likes Received:
    141
    Yes, and I do have some doubts about the results,

    but still

    RX64 voltage - 7,5%
    RX56 voltage - 11%

    performance similar up to 2-3%

    Power Consumption (whole System) RX56 reduced by 25% compared to the optimized RX64 - imho it does not add up. If there are no faults the measurement and the numbers are correct and disregarding the individual chip quality this strange.

    At the moment there are many unknowns. It seems there are at least 3 different versions of the GPU+HBM+Interposer package around, al slightly different and at least one with the HBM not being as high as the GPU, leaving a 0,1mm gap to the cooling solution. Also it seems like some test RX56 had Samsung HBM2 while those in retail show SK Hynix. At the moment RX Vega seems like a lottery to me.
     
    #1122 seahawk, Aug 23, 2017
    Last edited: Aug 23, 2017
    Entropy and Grall like this.
  3. entity279

    Veteran Regular Subscriber

    Joined:
    May 12, 2008
    Messages:
    1,229
    Likes Received:
    422
    Location:
    Romania
    with sample size = 1 (one v64, one v56) one can't draw such allarming conclusions
     
  4. ToTTenTranz

    Legend Veteran Subscriber

    Joined:
    Jul 7, 2008
    Messages:
    9,839
    Likes Received:
    4,456
    And why would you disregard chip quality?
     
    BRiT likes this.
  5. CarstenS

    Veteran Subscriber

    Joined:
    May 31, 2002
    Messages:
    4,797
    Likes Received:
    2,056
    Location:
    Germany
    They seem to have set PT+50% in the first place.
     
    Lightman, BRiT, pharma and 2 others like this.
  6. seahawk

    Regular

    Joined:
    May 18, 2004
    Messages:
    511
    Likes Received:
    141
    And yet the power consumption is measured as going down, which also makes me wonder.
     
  7. Grall

    Grall Invisible Member
    Legend

    Joined:
    Apr 14, 2002
    Messages:
    10,801
    Likes Received:
    2,172
    Location:
    La-la land
    What exactly is the power target slider doing anyway, raising max core voltage ceiling perhaps? I'm not sure I've ever seen a coherent explanation of this...
     
  8. entity279

    Veteran Regular Subscriber

    Joined:
    May 12, 2008
    Messages:
    1,229
    Likes Received:
    422
    Location:
    Romania
    It controls the throttling threshold, I think
     
  9. Grall

    Grall Invisible Member
    Legend

    Joined:
    Apr 14, 2002
    Messages:
    10,801
    Likes Received:
    2,172
    Location:
    La-la land
    Yes, but HOW does it do that? "With magic!" is a somewhat unsatisfying explanation... :D
     
  10. entity279

    Veteran Regular Subscriber

    Joined:
    May 12, 2008
    Messages:
    1,229
    Likes Received:
    422
    Location:
    Romania
    Well, knowing what your chip currently consumes would be all that's needed. There is on chip logic that performs these measurements / estimates.

    The throttling itself, when engaged, reduces the clocks and/or voltage.

    The algorithms themselves (for throttling and consumption computation) should be vendor specific and gpu-specific
     
  11. Rasterizer

    Newcomer

    Joined:
    Aug 4, 2017
    Messages:
    29
    Likes Received:
    9
    I believe the explanation is that RX64 is suffering much more severely from being front end bottlenecked by its polygon throughput still being on the order of 4 triangles per clock since primitive shaders have not been enabled in drivers yet. As a result the higher power target and CUs of RX64 are simply being wasted. RX56 is proportionally less effected by the front end bottleneck so its showing much better perf/watt even without primitive shaders enabled.

    That appears to be a typical result with undervolting Vega with an increased power target. Gamers Nexus found similar behaviour when they undervolted a Vega FE. With current RX drivers, it should be possible to do even better than what GN achieved as it should be possible to find a sub +50% power offset that is till high enough to allow the card not to power throttle at stock clocks while also undervolting.
     
  12. Malo

    Malo Yak Mechanicum
    Legend Veteran Subscriber

    Joined:
    Feb 9, 2002
    Messages:
    6,975
    Likes Received:
    3,051
    Location:
    Pennsylvania
    lol not this again. Where are you getting that now? The comment regarding the linux drivers?
     
    pharma likes this.
  13. Rasterizer

    Newcomer

    Joined:
    Aug 4, 2017
    Messages:
    29
    Likes Received:
    9
    [​IMG]

    The Vega whitepaper claims that primitive shaders can increase effective polygon throughput to up to 17 triangles per clock, but since 6,305/1630 = ~3.75 triangles per clock, either primitive shaders are not enabled yet in drivers or RTG made up the feature out of thin air and it doesn't actually exist. You'll also note that Vega 56 has exactly the same ~3.75 triangle per clock rate as RX64, which would be consistent with the performance testing done by many showing that RX56 delivers identical performance to RX64 at the same cocks.
     
  14. CarstenS

    Veteran Subscriber

    Joined:
    May 31, 2002
    Messages:
    4,797
    Likes Received:
    2,056
    Location:
    Germany
    So, primitive shaders have not been enabled in the drivers yet. Also, DSBR is not working for each and every application out there. Also, HBCC is disabled by default, even though it can potentially increase performance by double-digit percentages. Add all of that together (if those are accumulates) and you have your 1080 Ti competitor.
     
  15. sonen

    Newcomer

    Joined:
    Jul 13, 2012
    Messages:
    53
    Likes Received:
    33
    Typical result? Do we have a reasonable sample of undervolted Vegas to even talk about what's typical?


    Undervolted (1200->1025mV) and set to +50% power, Gamer's Nexus Vega 56 is drawing 30-70 Watts more than stock.

    [​IMG]
    http://www.gamersnexus.net/hwreviews/3020-amd-rx-vega-56-review-undervoltage-hbm-vs-core
     
  16. Malo

    Malo Yak Mechanicum
    Legend Veteran Subscriber

    Joined:
    Feb 9, 2002
    Messages:
    6,975
    Likes Received:
    3,051
    Location:
    Pennsylvania
    I believe this has been discussed before but the high polygon throughput is likely a potential based on culling primitives, not magically being able to generate more polygons than its 4 setup engines is capable of. That test you linked isn't designed to test any kind of discard from what I know.
     
    tinokun and pharma like this.
  17. pharma

    Veteran Regular

    Joined:
    Mar 29, 2004
    Messages:
    2,907
    Likes Received:
    1,607
    A Quick Look At The High Bandwidth Cache Controller On AMD’s Radeon RX Vega

    https://techgage.com/article/a-look-at-amd-radeon-vega-hbcc/
     
  18. Malo

    Malo Yak Mechanicum
    Legend Veteran Subscriber

    Joined:
    Feb 9, 2002
    Messages:
    6,975
    Likes Received:
    3,051
    Location:
    Pennsylvania
    I wonder if Raven Ridge will contain HBCC, potentially some improvements there to be had?
     
  19. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    8,166
    Likes Received:
    1,836
    Location:
    Finland
    No it won't. It might have similar functionality though, but HBCC needs that HBM "cache"
     
  20. xEx

    xEx
    Regular Newcomer

    Joined:
    Feb 2, 2012
    Messages:
    939
    Likes Received:
    398
    HBCC is more important with less VRAM Available but* we don't know if its useful at all without any VRAM available....HBCC for what I understand if just a way to only allocate the necessary data into the VRAM and "cache" the rest into system ram and trade them in real time.
     
Loading...

Share This Page

  • About Us

    Beyond3D has been around for over a decade and prides itself on being the best place on the web for in-depth, technically-driven discussion and analysis of 3D graphics hardware. If you love pixels and transistors, you've come to the right place!

    Beyond3D is proudly published by GPU Tools Ltd.
Loading...