AMD Vega 10, Vega 11, Vega 12 and Vega 20 Rumors and Discussion

Discussion in 'Architecture and Products' started by ToTTenTranz, Sep 20, 2016.

  1. Anarchist4000

    Veteran Regular

    Joined:
    May 8, 2004
    Messages:
    1,439
    Likes Received:
    359
    I was wondering the same thing and only thing I can think of is that Infinity also crossed for PCIe lanes with Epyc. Having more than 16 lanes would make sense for certain "server" parts that may link components via Infinity. Mostly related to SSG hosted controllers for NVMe or SAN. APU/x2 could be another possibility as could a larger PCIe slot. A 32 lane PCIe slot wouldn't be unreasonable with unified memory on server. Without serving as a means to connect chips, I'm at a loss for how it could be server optimized.
     
  2. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    8,183
    Likes Received:
    1,840
    Location:
    Finland
    If you're referring to early DX9-era hardware AMD went with FP24 on pixel shaders (vertex were always FP32), while NVIDIA supported little-less abysmally slow FP16 and abysmally slow FP32 for pixel shaders
     
  3. 3dcgi

    Veteran Subscriber

    Joined:
    Feb 7, 2002
    Messages:
    2,435
    Likes Received:
    263
    I feel like this has been discussed before, but I'm not sure what people think Radeons were lacking with respect to the ability to distribute geometry prior to Vega.
     
  4. sebbbi

    Veteran

    Joined:
    Nov 14, 2007
    Messages:
    2,924
    Likes Received:
    5,288
    Location:
    Helsinki, Finland
    Yes. However there's no guarantee for highp support for fragment shaders. You would get compile error on such GPU if you haven't programmed mediump code path for your fragment shaders. Also many mobile GPUs incur significant performance hit when highp is used, so it is good to use mediump even when you aren't targeting absolute low end.

    OpenGL ES 2.0 spec only guarantees >= 16 bits of mantissa precision for highp. This translates to minimum of 24 bit floating point (with exponent + sign bits). Thus you always need to ensure that 24 bit float precision is enough for your vertex shader work (similar to ATI DX9 GPUs). Mediump mantissa is guaranteed to be >= 10 bits, so it is at least as good as IEEE 16 bit float spec (10 bits mantissa, 1 bit sign, 5 bits exponent).

    Guaranteed integer support in OpenGL ES 2.0 is also limited to 16 bits (mantissa precision of minimum highp format). Thus you need to ensure that integer code runs properly with 16 bit integers. This kind of code is easy to port to desktop DirectX (min16int type is perfect fit for that).
     
    Heinrich4 likes this.
  5. sebbbi

    Veteran

    Joined:
    Nov 14, 2007
    Messages:
    2,924
    Likes Received:
    5,288
    Location:
    Helsinki, Finland
    AMD Vega marketing material tells us that Vega has improved geometry load balancing across multiple geometry engines. That already implies that something had to be improved :)
     
    Cat Merc, Picao84 and CarstenS like this.
  6. sebbbi

    Veteran

    Joined:
    Nov 14, 2007
    Messages:
    2,924
    Likes Received:
    5,288
    Location:
    Helsinki, Finland
    Fp16 wasn't abysmally slow on Nvidia 7000 series. Well optimized PS3 fp16 pixel shader code was faring pretty well against Xbox 360s ATI GPU. There was a free fp16 normalize instruction :). Old Nvidia GPUs however sucked in code with branches and EDRAM gave Xbox 360 a nice bandwidth boost.
     
  7. Rodéric

    Rodéric a.k.a. Ingenu
    Moderator Veteran

    Joined:
    Feb 6, 2002
    Messages:
    3,986
    Likes Received:
    846
    Location:
    Planet Earth.
    I assumed he talked about the GeForce FX though... (given it was the same era as R300 which was FP24)
     
    Lightman and Picao84 like this.
  8. Jawed

    Legend

    Joined:
    Oct 2, 2004
    Messages:
    10,873
    Likes Received:
    767
    Location:
    London
    AlBran, Cat Merc, Gubbi and 3 others like this.
  9. CarstenS

    Veteran Subscriber

    Joined:
    May 31, 2002
    Messages:
    4,798
    Likes Received:
    2,056
    Location:
    Germany
    Of course, I would love to learn more, but as far as I was being told, geometry and associated pixel stayed inside the shader engine to whose front end they were initially assigned edit: with the caveat, that there was a path for load balancing if required. In Tahiti (yes, older example), Wavefronts were generated from up to 16 primitives, but those had to reside in one screen tile (assigned to a shader engine). With Fermi, again AFAIK, geometry was (necessarily) redistributed after tessellation stage, because each SM is fetching vertices individually over a number of clock cycles.
     
    #3989 CarstenS, Sep 1, 2017
    Last edited: Sep 1, 2017
  10. sebbbi

    Veteran

    Joined:
    Nov 14, 2007
    Messages:
    2,924
    Likes Received:
    5,288
    Location:
    Helsinki, Finland
    Agreed. Geforce FX was awful. But Nvidia kept their fp16 + fp32 support for 6000 and 7000 series as well. 8000 was their first fp32 only product. PS3 was using Nvidia's last gaming GPU with fp16 support.
     
  11. Digidi

    Newcomer

    Joined:
    Sep 1, 2015
    Messages:
    225
    Likes Received:
    97
    Maybe we see improved geometry load balancing when Primitive Shader and DSBR are on and work together. For me it looks like Primitive Shader and DSBR is the optimized path for geometry load balancing and now we run on u unoptimized connections.
     
  12. 3dcgi

    Veteran Subscriber

    Joined:
    Feb 7, 2002
    Messages:
    2,435
    Likes Received:
    263
    What you were told isn't how I would explain it. Since multiple shader engines have existed geometry could always be processed on one shader engine and its output could be sent to another shader engine. This is a requirement since when the original geometry is distributed to shader engines the triangle screen coverage isn't known. The load balancing you were told about happens more often than not with 4 shader engines. To make it clear to others, the wavefronts "generated from up to 16 primitives" are pixel waves.

    Tonga was the first AMD chip that took tessellation factors into account when load balancing.
     
    CarstenS and Lightman like this.
  13. ToTTenTranz

    Legend Veteran Subscriber

    Joined:
    Jul 7, 2008
    Messages:
    9,966
    Likes Received:
    4,560
    Well I can confirm that MSAA performance in Vega is broken at the moment.

    I did some test runs in Deux Ex Makind Divided's internal benchmark @ 3440*1440, everything maxed out (really everything, just so there aren't any doubts), 105º FoV. Here are my average results using a Vega 64 in Power Save mode and a 10-core Xeon IvyBridge @ 2.9GHz:

    No MSAA - 44.5 FPS
    2x MSAA - 29.4 FPS
    4x MSAA - 19.5 FPS
    8x MSAA - 9.2 FPS

    These performance hits are typical of SSAA or downsampling/VSR. Something's not working right.
    Despite the game's constant warnings about VRAM usage with MSAA, it doesn't look like the game is topping the 8GB HBM2, as turning on HBCC with ~20GB allocated doesn't seem to make any difference.
    I would avoid using MSAA with this card at the moment for anything but older/simpler games.


    On the other hand, anisotropic filtering at 16x isn't taking any discernible performance hit over 8x, which is something that had been somewhat of a problem for prior GCN GPUs.
     
    #3993 ToTTenTranz, Sep 1, 2017
    Last edited: Sep 1, 2017
    T1beriu, Lightman, Cat Merc and 5 others like this.
  14. fellix

    fellix Hey, You!
    Veteran

    Joined:
    Dec 4, 2004
    Messages:
    3,489
    Likes Received:
    400
    Location:
    Varna, Bulgaria
    How is the image quality. Does it apply just MSAA or something more?
     
  15. pharma

    Veteran Regular

    Joined:
    Mar 29, 2004
    Messages:
    2,928
    Likes Received:
    1,626
    I may have missed it but did AMD directly comment on the MSAA issue and possible solution?
     
  16. Alessio1989

    Regular Newcomer

    Joined:
    Jun 6, 2015
    Messages:
    582
    Likes Received:
    285
    Worst NVIDIA geforce series ever, but best AGP 8x vacuum cleaner ever made.

     
    Lightman and AlBran like this.
  17. ToTTenTranz

    Legend Veteran Subscriber

    Joined:
    Jul 7, 2008
    Messages:
    9,966
    Likes Received:
    4,560
    To be honest in this game it's hard to tell. With everything cranked up to max the post effects hide the aliasing very well and TAA eliminates the little that is left. The difference between turning MSAA off or 8x is pretty much negligible in those conditions.
    I looked around for a bit in the game's last level, but I couldn't find any transparent texture by myself (which is where MSAA would be more noticeable).

    This is the best that I could do by turning off TAA, DoF bloom and lens flares:

    No AA -
    [​IMG]


    8x MSAA -
    [​IMG]



    I'll be happy to follow instructions on what to look for, or what graphics options to turn on/off to see this more clearly.
     
  18. Ethatron

    Regular Subscriber

    Joined:
    Jan 24, 2010
    Messages:
    859
    Likes Received:
    262
    Looks like MSAA isn't applied at all. Does the game even support it?
    Looking at this screen (t=190) I would say it doesn't resolve MSAA but simply pulls the first sample (look at the crane, it get fainter and fainter the higher the sample count, because it essentially degrades to point sampling), and doesn't support MSAA at all.
     
  19. 3dcgi

    Veteran Subscriber

    Joined:
    Feb 7, 2002
    Messages:
    2,435
    Likes Received:
    263
    Does Deus Ex MD support setting MSAA in game or is this forced in the driver?
     
  20. Rasterizer

    Newcomer

    Joined:
    Aug 4, 2017
    Messages:
    29
    Likes Received:
    9
    I've been reading up on the basics of how MSAA works, and as far as I can understand this as a beginner, doesn't MSAA involve rasterizing at a higher resolution than the intended display resolution? In which case, wouldn't MSAA performance be limited by rasterization rate? Doesn't that mean that Vega's presently being limited to four triangles per clock would negatively impact MSAA performance?
     
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...