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Playing >60Hz MAME games on a 4k FreeSync monitor (Windows)

Posted: 31 Dec 2017, 19:01
by chrispitude
Hi all,

I have an 32" Acer ET322QK 4k FreeSync monitor that I use to play MAME games with CRT shaders applied. Most games play very smoothly thanks to FreeSync, but I noticed that some games (such as Rally-X) still had some stuttering. I then discovered that these games all have refresh rates of 60.6Hz, and MAME's own FPS metric showed a steady 99% of target - just short.

This is not a MAME or a FreeSync limitation; DisplayPort 1.2 itself has a limit of 60Hz at 4k. However, I found a solution for Windows:
  1. Install Custom Resolution Utility (CRU) (https://www.monitortests.com/forum/Thre ... tility-CRU).
  2. In CRU, click "Edit..." to the right of the monitor name at the top, then change the maximum "V rate" value from 60 to 61.
  3. In CRU, under "Detailed resolutions", choose the 3840x2160 resolution, click Edit, and change the refresh rate near the bottom to 61Hz.
  4. Run the restart64 utility provided with CRU to restart your Windows graphics system.
  5. In the Windows display control panel, change the refresh rate to 61Hz. (In Windows 10, I did this at System > Display > Display adapter properties > Monitor tab > Screen refresh rate drop-down.)
  6. In your mame.ini file, set waitvsync to 1.

Re: Playing >60Hz MAME games on a 4k FreeSync monitor (Windo

Posted: 01 Jan 2018, 01:50
by RealNC
Yep. Doing this is really recommended. Not only for MAME, but for normal games too. In fact, if you can get it to 63Hz, or at least 62Hz, that would be optimal. You can then apply a 60FPS limiter which will reduce input lag by A LOT.

You might have to edit the freesync range too though to get the benefit. Not sure. You can edit in CRU (there's a button to edit monitor information, and the freesync range is in that dialog.)

Re: Playing >60Hz MAME games on a 4k FreeSync monitor (Windo

Posted: 01 Jan 2018, 11:12
by Chief Blur Buster
RealNC wrote:Yep. Doing this is really recommended. Not only for MAME, but for normal games too. In fact, if you can get it to 63Hz, or at least 62Hz, that would be optimal. You can then apply a 60FPS limiter which will reduce input lag by A LOT.

You might have to edit the freesync range too though to get the benefit. Not sure. You can edit in CRU (there's a button to edit monitor information, and the freesync range is in that dialog.)
If frame pacing in MAME is extremely accurate, 61Hz or even 60.5Hz may work.

The headroom is just needed to accomodate random individual frametime fluctuations (frametimes faster than a refresh cycle), but since it is already a low Hz, a single Hz headroom works better at 60Hz than at 240Hz. Some (not all) emulators have impeccable frame pacing so tighter VRR headroom is sometimes doable.

Another technique for 60Hz VRR monitors is to intentionally slow down MAME to emulate ~98% its original speed (If there is a way to do so) making it run at 59.0fps, for monitors with VRR ranges that end at 60.0Hz. Sounds will be slightly lower pitched, but this is another theoretical way to reduce input lag on VRR monitors limited to max 60.0Hz. That said, some will overclock a bare bit higher than 60Hz. Even 60.5Hz will be much better than nothing - reducing emulator lag noticeably.

If buying anew for low-lag emulator use, I do recommend a VRR range that goes up to 75Hz (or more). Much simpler.