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  1. passenger

    passenger Master Guru

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    I have AOC with freesync range 38-75Hz, and lfc kicks in at 37Hz. Is there any way to force LFC, in drivers or some util, to start at 38Hz?
     
  2. iakoboss7

    iakoboss7 Active Member

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    pretty sure we have the same monitor ( Q3279vwfd8 ), i have the exact same problem/question.

    the monitor flickers bellow 38hz/fps if anyonce can help it would be appreciated.
     
  3. RealNC

    RealNC Ancient Guru

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    38*2 = 76Hz. The display does 75Hz, so it can't start LFC at 38.

    You can try and do a small overclock though. Maybe you can bump it up by a couple Hz using ToastyX CRU. You also need to edit the freesync range in CRU after that.

    None of this is guaranteed to work, mind you.
     
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  4. z8373767

    z8373767 Member Guru

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    Try CRU
    Do it in steps. I mean set 35Hz, if works go lower etc.
    [​IMG]

    You can skip step 3. It's not required.
    29Hz LFC works for me.
     
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  5. OnnA

    OnnA Ancient Guru

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    Or just set FS at 30-75 ;)
     
  6. iakoboss7

    iakoboss7 Active Member

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    guys, if he has the monitor i am talking about, the 38-75 is the limit using CRU... the monitor normally is 48-75.
    setting freesync range bellow 38 the monitor flickers.
     
  7. mtrai

    mtrai Master Guru

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    If you are getting flickering at 37 then see if you up the max range. Use CRU to do this. You will have to add a detailed resolution. So try 80 for your refresh rate...heck I would see how high I could set the upper refresh rate limit. AKA overclocking your monitor.
     
  8. iakoboss7

    iakoboss7 Active Member

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    thank you, forgot to mention i have already tried that. it will not go even at 76hz.
    actually it can get to 76 (but not higher) if i select 8bit, disable gpu scaling and use limited rgb. (not worth it).

    thats why we need a way to force lfc.

    for anyone that is interested there is a lengthy discussion here: https://www.overclock.net/forum/44-...1-5-ips-2560x1440px-75hz-adaptive-sync-4.html

    i hope i am not bothering the OP (and i also hope he has the same monitor as me, cause i am just guessing with the the info provided).
     
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  9. passenger

    passenger Master Guru

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    Yep D8, it’s better than my old 650€ Asus mg279q.

    It needs to be done on driver level, that's the reason I was asking. It can be oced to 76Hz and underclocked to 38Hz but problem is that lfc in this case starts at 37Hz sadly. So monitor can do 38*2 but that 2x range is not enough for lfc. I hope that there is a way to acitvate lfc in that fereesync range,it's only 1Hz maybe AMD can forgive us:)
     
  10. OnnA

    OnnA Ancient Guru

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    FreeSync 2: Low Framerate Compensation

    The final key feature is low framerate compensation. This is a feature that goes hand-in-hand with adaptive sync, ensuring adaptive sync functions at every framerate from 0 FPS up to the maximum refresh rate supported by the display.

    There is one simple reason why we need low framerate compensation: displays can only vary their refresh rate within a certain window, for example 48 to 144 Hz.
    If you wanted to run a game below the minimum supported refresh rate, say at 40 FPS when the minimum refresh is 48 Hz, normally you’d be stuck with standard screen tearing or stuttering issues like you’d get with a fixed refresh monitor.
    That’s because the GPU’s render rate is out of sync with the display refresh rate.

    [​IMG]

    Low framerate compensation, or LFC, extends the window in which you can sync the render rate to the refresh rate using adaptive sync.
    When the framerate falls below the minimum refresh rate of the monitor, frames are simply displayed multiple times and the display runs at a multiple of the required refresh rate.

    In our previous example, to display 40 FPS using LFC, every frame is doubled and then this output is synced to the display running at 80 Hz.
    You can even run games at, say, 13 FPS and have that synced to a refresh rate; in that case the monitor would run at 52 Hz (to exceed the 48 Hz minimum) and then every frame would be displayed 4 times.

    The end result is LFC effectively removes the minimum refresh rate of adaptive sync displays, but for LFC to be supported, the monitor needs to have a maximum refresh rate that is at least double the minimum refresh rate.
    This is why not all FreeSync monitors support LFC; some come with just 48 to 75 Hz refresh windows, which doesn’t meet the criteria for LFC.
    However in the case of FreeSync 2, every monitor validated for this spec will support LFC so you won’t have to worry about the minimum refresh rate of the monitor.

    -> https://www.amd.com/Documents/freesync-lfc.pdf

    I hope it helps.
    IMO it must be LFC Feature on H/W level of the monitor.
    If monitor supports it, it will work, no matter the settings for FS.
    It will work at 0,1,2,3 etc. FPS/Hz also, do not confuse FS range with LFC.
     
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  11. iakoboss7

    iakoboss7 Active Member

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    thank you, those are known, amd states it needs the top freesync range to be x2.5 the minimum for lfc to work. actually its allot lower, closer to x2 (x2+1hz i think).

    thats why with 38-75hz range we cannot have lfc. but our monitor flickers bellow that and cant be overclocked higher (except if you sacrifice many things, to gain only 1hz).
     
  12. user1

    user1 Maha Guru

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    trying to do this type of compensation with less than 2x simply cannot work completely as there will be a gap where it doesn't work, so in your case 38-75 there is a gap between 37.5 and 38 where the refreshrate cannot be doubled to compensate. is it possible that amd could add the ability to do frame pacing to avoid the gap? , probably , but as it currently stands there is no implementation for this.
     
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  13. Benik3

    Benik3 Master Guru

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    I wanted to try downclock/overclock my LG 27MP68HM-P monitor (CRU, VSR), but I always got "HDMI Out of Range" :/
    Even when I tried 40Hz which should be supported by default.
    My monitor has only 40-75Hz FreeSync range.
    BTW in the AMD document there is that the max frequency should be even >= 2,5x minimal to get LFC to work o_O
     
  14. nikobellic

    nikobellic New Member

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    Can you try "LCD reduced" instead of "LCD native" when you try to overclock your monitor to 76Hz? My monitors freesync range is also 40-75Hz, but I could make this range to 38-76Hz (LCD reduced). And now LFC works, but there is a problem, if I try any driver released after18.6.1, I see flickering and huge screen tearing whenever fps drops below 38fps. So, I am still sticking with 18.6.1
     
  15. Benik3

    Benik3 Master Guru

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    Nope, but I just found another interesting thing.
    When I set 40FPS, I see tearing (pattern test in nvidia Pendulum). The tearing is here until it hit 44FPS.
    But when I go from higher FPS, it's OK until it hit the 40FPS, where tearing starts again.
    Also enhanced sync works pretty OK for FPS over screen, but there are lags. Without sync, FPS over frequency is with big tearing (even 150FPS which is 2x max frequency).
     

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