Anti-Lag Thread

Discussion in 'Videocards - AMD Radeon Drivers Section' started by Eastcoasthandle, Jul 10, 2019.

  1. Microsista

    Microsista New Member

    Messages:
    5
    Likes Received:
    1
    GPU:
    Gigabyte RX 580 8GB
    where exactly is this backpressure coming from? is it because with a fps cap the cpu knows to start rendering exactly every 16.(6)ms (in case of a 60fps cap), and without a cap it has to wait for the information from the gpu when to start rendering same as with vsync?

    EDIT: also in case of a lack of in-game fps cap, or a terrible implementation (like in bfv for example, where it alternates between 19.7 ms, and 13.7 ms each frame, and that doesnt feel smooth at all) should i use RTSS cap (which the worst capped solution since it introduces additional lag), or uncapped with anti-lag (which is the best case for uncapped since it reduces lag), im guessing the first option will still be snappier? from just testing i really cant tell the difference...
     
    Last edited: Sep 25, 2019
  2. RealNC

    RealNC Ancient Guru

    Messages:
    3,142
    Likes Received:
    1,369
    GPU:
    EVGA GTX 980 Ti FTW
    @Microsista

    Yep. Pretty much that. A cap keeps the CPU in sync with the GPU. The submission of work from the CPU to the GPU is asynchronous these days (I think the last time it was synchronous was in the PS1-era or somewhere around that.) This means the game is allowed to start preparing the next frame after submitting the current one to the GPU for rendering. The CPU hopes that by the time it will submit the next frame for rendering, the GPU will have finished rendering the one it submitted just now. But if that's not the case and the GPU can't finish the work in time (because vsync is blocking it from doing so, or because the GPU just can't process any faster,) the CPU has to wait even though the game has already read input from the player.

    Waiting means that input gets older and older. Old input that is processed too late is the cause of input lag. By the time the GPU finally finished and accepts the next prepared frame to be rendered, that frame is based on very old player input. And by the time the GPU finishes actually rendering it, it's even older. So you get a lag pile-up.

    Lowering MPRF reduces that pile-up. With an MPRF of 1, the game can be 2 frames behind the GPU. The one allowed by an MPRF of 1, and another one that is the result of the game being blocked because it read input for frame 2, but is prevented from preparing that frame because only 1 pre-rendered frame is allowed.

    The "low lag" setting can help with reducing a large portion of 1 frame of lag, but that's it. It will not prevent the backpressure caused by the game reading player input and then sitting on that input for a long time because the GPU is bottlenecking it.

    A frame cap on the other hand is much more aggressive. It prevents the game from reading input too soon and thus can get rid of both frames of lag. Or any other additional buffering that might be happening internally by the game, the OS or the GPU driver. If the GPU isn't ready to process the next frame (meaning at 60FPS 16.7ms haven't passed yet,) the game will do nothing but wait until the GPU is ready to render more. This gets rid of both frames of lag. The cap will not allow any buffers to be filled and bottleneck the whole pipeline.

    The other way to look at it is that a cap prevents the CPU from running ahead of the GPU. There can be no bottleneck. Unless of course your cap is set too high, in which case the GPU can reach its maximum and thus bottleneck the CPU.
     
    Last edited: Sep 25, 2019
    yasamoka likes this.
  3. Microsista

    Microsista New Member

    Messages:
    5
    Likes Received:
    1
    GPU:
    Gigabyte RX 580 8GB
    so using MATH (assuming 60 fps):
    uncapped MPRF1 = 2 frames ~33.(3) ms of additional lag
    uncapped anti-lag = 1.2 frames ~20 ms of additional lag
    rtss cap = 1 frame ~16.(6) ms of additional lag
    in-game cap = 0 frame ~0 ms of additional lag
    which is probably why i couldn't tell the difference between anti-lag and rtss cap
     
  4. RealNC

    RealNC Ancient Guru

    Messages:
    3,142
    Likes Received:
    1,369
    GPU:
    EVGA GTX 980 Ti FTW
    @Microsista

    I suspect that there's probably also some unknowns there too. Like internal buffering by the game, the OS or the GPU driver that can only become visible when there's a bottleneck. If true, these are probably impossible to actually quantify.

    And different games do different things. If a game reads input too early, lag is higher when there's a GPU bottleneck. But if the game reads input as late as possible, it would have less lag.
     

  5. Eastcoasthandle

    Eastcoasthandle Ancient Guru

    Messages:
    2,592
    Likes Received:
    359
    GPU:
    Nitro 5700 XT
    Everything still working well with Anti lag.
    I did pickup on something though which I believe might be my own preference.
    I realize that I need to add a smidgen of mouse acceleration to get movement the way I want it. We are talking less then 0.15 in COD games. Problem is that is the only game that allows increments like that. But it's very good for full 180 degree rotations which are bang on consistent now.

    I wish there was a way to enable a mouse acceleration slider in win10 like that.
    (R9 Fury)
     
    Last edited: Oct 14, 2019
  6. Supertribble

    Supertribble Master Guru

    Messages:
    658
    Likes Received:
    45
    GPU:
    1080Ti/RadVII/2070S
    Does anti lag work with dx12 and vulkan? I swear I had it working with the division dx12 at one point but now it doesn't. also, i can't get it working with doom (vulkan). I could be losing my mind with the division tho.
     
  7. SpajdrEX

    SpajdrEX AMD Vanguard

    Messages:
    2,327
    Likes Received:
    627
    GPU:
    RTX2070 SUPER
    You would need to run Division 1/2 in DX11 to get anti-lag to work.
    But in the case of Division 2, it has its own anti-lag feature.
    Anti-lag only works for DX11 games and DX9 games (if you have RX5700 series card), at least for now.
     
  8. Supertribble

    Supertribble Master Guru

    Messages:
    658
    Likes Received:
    45
    GPU:
    1080Ti/RadVII/2070S
    Ok, thanks for clearing that up. :)
     
  9. gabsvm

    gabsvm Member Guru

    Messages:
    114
    Likes Received:
    19
    GPU:
    RX 580 8gb
    This works with emulators like Tencent Gaming Buddy, Dolphin?
     
  10. Astyanax

    Astyanax Ancient Guru

    Messages:
    6,955
    Likes Received:
    2,222
    GPU:
    GTX 1080ti
    no
     

  11. gabsvm

    gabsvm Member Guru

    Messages:
    114
    Likes Received:
    19
    GPU:
    RX 580 8gb
    Last edited: Oct 23, 2019
  12. Kulagin

    Kulagin Member

    Messages:
    47
    Likes Received:
    3
    GPU:
    R9 280X
  13. Kulagin

    Kulagin Member

    Messages:
    47
    Likes Received:
    3
    GPU:
    R9 280X
    Thanks for tips. How do I disable auto power management for the GPU and use manual settings?
     
  14. Kulagin

    Kulagin Member

    Messages:
    47
    Likes Received:
    3
    GPU:
    R9 280X
    So where do these 30+ ms of lag come from? Does buffer pileup means much more work for CPU/RAM/GPU to store this buffer and then read it back? Where is this buffer stored? In RAM? In VRAM?
     
  15. ATi7500

    ATi7500 Member

    Messages:
    30
    Likes Received:
    0
    GPU:
    R7 Graphics
    What about when Vsync is ON? A Frame cap makes a difference ONLY when is below refresh rate?
     

  16. Eastcoasthandle

    Eastcoasthandle Ancient Guru

    Messages:
    2,592
    Likes Received:
    359
    GPU:
    Nitro 5700 XT
    Here is some interesting tidbits about the difference between FRTC and Chill

    This is only povided so that you read the comments, not the video itself.
     
  17. connos

    connos Maha Guru

    Messages:
    1,238
    Likes Received:
    41
    GPU:
    AMD 5700XT
    Interesting. From were did you get this info?
     
  18. Eastcoasthandle

    Eastcoasthandle Ancient Guru

    Messages:
    2,592
    Likes Received:
    359
    GPU:
    Nitro 5700 XT
    In the comments of the video
     
  19. Jayson

    Jayson Active Member

    Messages:
    67
    Likes Received:
    13
    GPU:
    Radeon RX 580 8GB
    Can someone test Anti-Lag in Rocket League? With AL now available for RX 580, it would be interesting to know if AL gives any sort of advantage in Rocket League. I play at 1440p by the way, so I might be GPU bound in that particular title.
     
  20. lolitro

    lolitro New Member

    Messages:
    3
    Likes Received:
    2
    GPU:
    AMD RX570
    Radeon anti lag is good for csgo and valorant, fps games? Or is bad for fps max uncapped?

    Anti lag is worth with main3d 1?
     

Share This Page