MiSTer FPGA Forum

Posted: **Tue Nov 03, 2020 3:42 pm**

Do freesync monitors work with MiSTer?

okay I need more words.

Freesync monitors are modern LCD/OLED/whatever displays that can run at a range of refresh rates similar to the CRTs we all love and adore. I have one on my main PC that'll do 45-75.

I know a lot of arcade games had weird refresh rates and didn't know if this would be compatible.

Posted: **Tue Nov 03, 2020 4:08 pm**

The monitor would work yes but without using any free/adaptive/G/sync.
Before i bought my mister in july and some months before that i read around that many thought that any sync monitor would be better since they probably would handle strange/slightly sync/refresh rates better.

And i already had a AOC ag271qg (1440p165hz gsync) and thought perfect.
But i can not get anything higher then 1080p to work at all and i really want 1440p since it scale better with integer scaling (a bit bigger picture then 1080p).

Posted: **Tue Nov 03, 2020 6:08 pm**

grizzly wrote: ↑Tue Nov 03, 2020 4:08 pm But i can not get anything higher then 1080p to work at all and i really want 1440p since it scale better with integer scaling (a bit bigger picture then 1080p).

When you say it wasn't working, what do you mean specifically? No image or a stretched image? If the image is stretched or not sized correctly, you need to either adjust the settings on your monitor's control panel or something may be off in the custom resolution you would have to set for 1440p (https://www.retrorgb.com/mister-1440p-1 ... aling.html).

Posted: **Tue Nov 03, 2020 9:36 pm**

I mean no picture at all.
Tried every modline i can find online, tried my own modline calculated from the monitors extracted EDID data, but nothing over 1080p gives any picture.

Posted: **Sat Nov 07, 2020 4:31 pm**

I have a FreeSync/G-Sync Compatible monitor (LG 27GL83A-B) and it's worked fine with MiSTer at 1920x1440, with or without Adaptive Sync enabled. It does drop out for a second or two after starting up a game with vsync_adjust=2 enabled, presumably due to the refresh rate switch. It would be nice if more cores offered a "Sync core to video" option like the GBA core, I don't get the dropouts when launching GBA games with that enabled and the minuscule speed difference doesn't bother me.

Posted: **Sat Nov 07, 2020 5:42 pm**

justaguy wrote: ↑Sat Nov 07, 2020 4:31 pm I have a FreeSync/G-Sync Compatible monitor (LG 27GL83A-B) and it's worked fine with MiSTer at 1920x1440, with or without Adaptive Sync enabled. It does drop out for a second or two after starting up a game with vsync_adjust=2 enabled, presumably due to the refresh rate switch. It would be nice if more cores offered a "Sync core to video" option like the GBA core, I don't get the dropouts when launching GBA games with that enabled and the minuscule speed difference doesn't bother me.

Okay - had the time today to actually plug a MiSTer into a Freesync monitor, and gloriously it appears the adaptive frame rate matching seems to work.

It's an Acer SB220Q, 1920x1080. Supports FreeSync. It has an option to display the current frame rate as on overlay, which I turned on.

Most games displayed the expected 60fps, I switched to Neo-Geo and it displayed 59fps. Jumped to Megadrive/Genesis and loaded up Gods and Chaos engine. After switching the region to PAL, got 50fps. Did the same for Super Turrican on PAL NES. 50fps.

Displayed with no tearing or other issues every time. vsync adjust is set to 2, which is low lag.

Later tonight I'll do some display lag testing with crts I have as a comparison.

TLDR; freesync works great

Posted: **Mon Nov 09, 2020 3:34 am**

That is great news! Since the monitor is listed with a max of 75hz, I am curious about 70hz DOS games displaying smoothly.

Posted: **Mon Nov 09, 2020 4:48 am**

justaguy wrote: ↑Sat Nov 07, 2020 4:31 pm I have a FreeSync/G-Sync Compatible monitor (LG 27GL83A-B) and it's worked fine with MiSTer at 1920x1440, with or without Adaptive Sync enabled. It does drop out for a second or two after starting up a game with vsync_adjust=2 enabled, presumably due to the refresh rate switch. It would be nice if more cores offered a "Sync core to video" option like the GBA core, I don't get the dropouts when launching GBA games with that enabled and the minuscule speed difference doesn't bother me.

Try vsync_adjust=1, I think you'll like it

Posted: **Mon Nov 09, 2020 3:15 pm**

It seems to work on my TV with freesync on... if I add that plus game mode and switch off all processing options, and vsync_adjust=2, then I get roughly 2.5-3 frames of lag compared to my CRT (measured by taking a picture of my CRT next to my LCD TV using the 240p test suite).

That's much better than the 6-7 frames of lag I got originally before I tried to optimize anything.

Posted: **Mon Nov 09, 2020 7:49 pm**

Did some display lag testing - 240p test suite NTSC shows less than one frame of display lag when running with low lag mode.

: RihvXkH.jpeg (303.36 KiB) Viewed 8984 times

Also tested out lunar lander which I understand has a weird refresh rate and won't display on my CRT. Ran flawlessly. (I assume the flickering was part of the vector display.)

I also took a slowmo video of it dropping to 50hz to run the PAL 240p test suite. Once again my CRT wouldn't display it, but the slowmo indicated no tearing whatsoever.

Posted: **Wed Feb 17, 2021 4:58 pm**

Hi all,

I assume that you’re all using the HDMI port on the freesync monitors vs the VGA (DB15) port. I’ve got an analog IO board on my MiSTer which I have running to my 27” Sony CRT TV. This works beautifully for most horizontal based 240p games. I run the HDMI out to my Acer ET322QU monitor, but couldn’t get it to show anything other than 60fps when I tried this yesterday. I use direct_video=1 in the CRT focused ini file and direct_video=0 for the HDMI focused ini file. Any advice for a newbie on getting refresh rates other than 60Hz on a freesync monitor would be greatly appreciated.

Thanks,
Bret

Posted: **Wed Feb 17, 2021 8:23 pm**

Hi Bret, I would try direct_video=1. This will give zero lag and native frame rates and resolution to the monitor. I don't know whether the monitor can display that or not, and whether the monitor will add any lag after it receives the signal. Keep in mind there is no scaler used here, so the image might be stretched in a bad way on the monitor. If that is the case, see the below.

If that doesn't work, you can use direct_video=0 and then adjust the vsync_adjust value to 2 for the lowest latency. If that doesn't work, try setting it to 1. With this mode, you can set the resolution to whatever you want and scale it properly.

Hope this helps and works for you.

Posted: **Wed Feb 17, 2021 9:10 pm**

Awesome! Thanks Thorr. I’ll give that a shot. I’ll let everyone know what works best.

Posted: **Wed Feb 17, 2021 10:21 pm**

Vsync_adjust=2 is defiantly producing the intended effect! I’m having problems with the power on MiSTer menu with the display not holding. I tried several video_modes attempting to create a 1920x1440 display, but the monitor keeps losing sync. Does anyone have a good 1920x1440 modeline that you’d like to share? I’ve tried:

video_mode=1920,48,32,112,1440,3,4,39,184828

video_mode=1920,32,32,50,1440,4,5,26,180000

But both fail to hold. I continue to revert back to the stock 1920x1080 (video_mode=8) for the menu and most games. I’ve been using the 5x settings provided recently by Atrac17 on the MisterFPGA Twitter feed for things like cps 1/1.5/2 SMS, Genesis, TG16, and NeoGeo with great results. His custom modelines work without a problem.

Thanks!

Posted: **Fri Mar 26, 2021 1:43 pm**

How hard would it be to support Freesync, if possible at all? As far as I understand, this would require a fixed pixel clock (say corresponding to 60Hz) with a variable vertical blank period. But I might misunderstand the Freesync standard.

Support for Freesync has the advantage of supporting a widely accepted standard. It seems increasingly difficult to find monitors that support all the, nowadays, odd frequencies that retro computers produce. Almost all Freesync monitors support at least 40-60 Hz, covering almost all retro computers. Another benefit would be the possibility to instantly change the refresh rate, without the need to resync, as this is essentially the purpose of Freesync. This could be especially beneficial for cores that (slightly) change the refresh rate on the fly, like Minimig for example. The monitors I found that do support a variable pixel clock, unfortunately require quite some time to resync.

I'm very thankful voor the Mister as it is. It's fantastic to relive my childhood computers again!
Since I can't code Verlig/VHDL, this is by no means a request. I was just wondering if it's possible. I

Thanks!

Posted: **Fri Mar 26, 2021 9:04 pm**

Kintaro wrote: ↑Fri Mar 26, 2021 1:43 pm How hard would it be to support Freesync, if possible at all? As far as I understand, this would require a fixed pixel clock (say corresponding to 60Hz) with a variable vertical blank period. But I might misunderstand the Freesync standard.

Support for Freesync has the advantage of supporting a widely accepted standard. It seems increasingly difficult to find monitors that support all the, nowadays, odd frequencies that retro computers produce. Almost all Freesync monitors support at least 40-60 Hz, covering almost all retro computers. Another benefit would be the possibility to instantly change the refresh rate, without the need to resync, as this is essentially the purpose of Freesync. This could be especially beneficial for cores that (slightly) change the refresh rate on the fly, like Minimig for example. The monitors I found that do support a variable pixel clock, unfortunately require quite some time to resync.

I'm very thankful voor the Mister as it is. It's fantastic to relive my childhood computers again!
Since I can't code Verlig/VHDL, this is by no means a request. I was just wondering if it's possible. I

Thanks!

Freesync, as well as Gsync, are proprietary tech which needs the 'handshake' of an OS driver to operate.

Take a look at this post viewtopic.php?f=33&t=2113. This thing syncs with everything I'd imagine!

Posted: **Fri Mar 26, 2021 9:35 pm**

Most modern freesync monitors will 'just work' when you enable adaptive sync and plug a mister in. It will display whatever refresh rate the mister is sending, assuming it is within the supported range of the monitor. I've verified on my LG displays that it is driving the output at the input refresh rate via the factory service menu(s). Just make sure you have vsync_adjust=2 in the ini jfile.

It will likely just fail to display if the refresh rate is out of the supported range, but most panels go down to like 48Hz so you're likely to always be above that.

You're right that the resync time is a pain, and that if a core changes refresh rate it's likely going to recalculate the pixel clock and trigger a resync. It might be possible to mitigate it somehow. The vast majority of the cores are fixed refresh rate so there's probably going to be some inertia to starting that type of work.

I have no idea if the old g-sync monitors will work like this. They had an nvidia proprietary hardware module in the monitor, so it's probably a no-go. I'm not even sure they still sell those anyways.

Posted: **Fri Mar 26, 2021 9:44 pm**

lamarax wrote: ↑Fri Mar 26, 2021 9:04 pm Freesync, as well as Gsync, are proprietary tech which needs the 'handshake' of an OS driver to operate.

Freesync is royalty-free and free to use. The HDMI implementation of the standard is known as HDMI Variable Refresh Rate, or VRR, and is only part of the HDMI 2.1 standard - which the MiSTer does not support. It is sometimes implemented in HDMI 2.0, but MiSTer also doesn't support that version of the standard.

Reference

Posted: **Sat Mar 27, 2021 4:41 am**

BTW, a quick way to test if your monitor is actually displaying at the proper refresh rate when you set vsync_adjust=2:

Load the NEO GEO core, and then load Samurai Shodown II. Wait for the demonstration to start, and look at the shadows under the characters.
When the refresh rate is correct, you should see the shadow flickering fast. When the refresh rate is wrong, the flickering will be uneven: sometimes it will go completely black or completely disappear for a frame or two.

Change between vsync_adjust=0 and vsync_adjust=2 to see if there's a difference for you.

If we ever get a Mortal Kombat core that is a good game to test too: the fast scrolling of all the character portraits should be 100% smooth on a properly functioning freesync display. Otherwise if the input and display refresh rates are mismatched it will stutter.

Posted: **Sun Mar 28, 2021 5:48 pm**

Posted: **Mon Apr 05, 2021 2:13 pm**

I wonder, does any one have try a Freesync monitor with vsync_adjust=1 yet? I've got an old (2008) Toshiba Tekbright monitor that I can drive at any native core refresh (vsync_adjust=1) upscaled to the panel native resolution (1680x1050). Beside being old and a fading backlight, this thing is glorious for displaying games like Dodonpachi @ 57hz or weird PAL Atari 2600 games. Does anyone got a modern equivalent of a real multi-sync monitor?

Posted: **Fri Apr 09, 2021 3:43 pm**

Seems like the trick is whether they can accept freesync over HDMI and what their true range is. I've got a 27UD68 that only supports freesync over DP so I haven't gotten that to sync with mister. You can submit odd refreshes but it always renders to 60. Meanwhile a newer MSI G273QF does sync perfectly over HDMI, but its minimum refresh isn't quite low enough to run PAL games. (When running on a PC with retroarch its actually shooting up into the 100s I.E. Low Framerate Compensation.) So I have to make a 100hz video mode to get PAL running smooth but that invites a bit of lag with vsync_adjust=0.

But yes I also have a real old 1920x1200p LCD, no freesync capabilities whatsoever, and it can sync between 45 and 85 hz perfectly, although it won't go beyond 60 at 1200p. It took a while for 60hz to become standard with so many 70hz dos applications, so there's good odds that old enough LCDs can handle multiple refreshes properly.

Posted: **Tue May 04, 2021 5:42 pm**

I'm assuming this is impossible on a LG CX despite it having Freesync? Using the green VRR button it reports what the core is running e.g. Neo geo at 59 and Snes at 60.10 but it says 'FIXED' and assume it isn't running as it only supports free and g sync through HDMI 2.1 which Mister doesn't support. On SS2 on the Neo despite it reporting the 59hz refresh rate the shadows flicker incorrectly and the background scroll pauses every few seconds very very briefly. On my old freesync monitor with mame and a dvi lead this didn't happen. I'm assuming the culprit is the TV but I'd like to know for sure.

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