There are two main resolutions for DOS games, 640x480@60Hz and 640x400@70Hz.

I created a custom resolution 640x400 @ 70Hz with nvidia and in dosbox set the Fullscreen resolution to Original, scaler=scale2x, aspect=false.
This will change the output resolution according to the actual game resolution.
I have connected a CRT with a DVI to VGA adapter and the game looks EXACTLY like on my dos machine with all the correct resolutions and refresh rates.

The next best thing would be an IPS with variable refresh rate, like the Gsync or Freesync monitors available.
You just create a 640x400@70Hz custom resolution in your GPU driver and that's it.

I've got a Yamakasi Catleap Q270 that can overclock to about 110hz before artifacts appear. I use EVGA Precision to adjust the pixel clock.

Yes, but can it run Supaplex without stuttering?

EDIT: I should mention that when it comes to retro, having the biggest "brain" doesn't mean poop. 😎

James-F wrote:

Yes, but can it run Supaplex without stuttering?

EDIT: I should mention that when it comes to retro, having the biggest "brain" doesn't mean poop. 😎

I can't tell who in this thread you are talking to that would make sense. Did you reply to the wrong thread?

jonnyjr wrote:

Actually, DOS games do not run at exactly 60 or 70 hz, but at 59.713 or 70.086 Hz... use DosBox video recording to get the actua […]
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ZellSF wrote:

...
Firstly, Epic Pinball runs at 60 frames per second (the menus run at 70 though), so if you used that to measure if your screens work at 70hz...
...

Actually, DOS games do not run at exactly 60 or 70 hz, but at 59.713 or 70.086 Hz... use DosBox video recording to get the actual screen refresh rate(s) the game is using.

I've used Nvidia custom resolution to set my refresh rate to these refresh rates, and when running DosBox in a window (I haven't found any way to force DosBox refresh rate in fullscreen) I get very smooth playback without stuttering. However, if the game changes refresh rate (as Epic Pinball and Jazz Jackrabbit does), I have to select the refresh rate that is used most of the time.

I'm curious about whether FreeSync/G-Sync will solve these problems or not, so I'm going to buy a FreeSync monitor and check it out in the near future.

G-Sync definitely does solve this problem. Unsure about FreeSync.

And yes, obviously the refresh rates are not exactly 60 or 70hz, but it's easier to type and no one's getting confused.

Here's some useful info for nvidia users:

Vsync can be enabled for dosbox to eliminate tearing by turning Vsync ON in nvidia control panel instead of "Use the 3D application settings", because dosbox never calls for Vsync.
When dosbox set to OpenGL the fulldouble setting does nothing, and Vsync is always On by the nvidia CP.
When dosbox set to Ddraw the fulldouble is a Vsync On/Off switch for dosbox, but Vsync ON has to be also set in nvidia CP, else fulldouble does nothing.

Important;
Enabling Vsync in dosbox with a fixed 60Hz monitor (not Gsync or CRT) destroys 70Hz games timing and music.
Games like Epic Pinball, Supaplex, Mortal Kombat 3, (and countless other 640x400 games) which run at 70Hz now run in 60Hz and have severe timing issues with the audio but the video is silky smooth.

If you have a CRT the absolutely best settings for dosbox to behave like real dos would:
output=opengl
fullresolution=original
aspect=false
scaler=normalx2
In nvidia CP create two custom resolution with DMT timing: 640x480@60Hz and 640x400@70Hz, make sure you set Vsync and Triple Buffering to ON.

If you have a GSync monitor:
output=opengl (specifically not openglnb).
fullresolution=desktop
aspect=true
scaler=normalx3 forced (this is the important part).
In nvidia CP set vertical sync to G-Sync.

If you have an LCD that does 70Hz without frame skipping (overclockable) and is a 4:3 or can be forced to 4:3:
Use the same settings as for the CRT but keep in mind that you'll use the LCD scaler and the image will not be as sharp (blurry).
There is no point in creating a native resolution 70Hz mode because dosbox will not switch to that unless specified as fullresolution, only "Original" will switch resolutions.

Note to dosbox Devs:
If there would be two separate fullresolution options for x400@70 and x480@60 modes that would be a life saver for LCD screens with overclockable (non-locked) refresh rate.

James-F wrote:

Important;
Enabling Vsync in dosbox with a fixed 60Hz monitor (not Gsync or CRT) destroys 70Hz games timing and music.
Games like Epic Pinball, Supaplex, Mortal Kombat 3, (and countless other 640x400 games) which run at 70Hz now run in 60Hz and have severe timing issues with the audio but the video is silky smooth.

Again, Epic Pinball = 320x240@60hz. Only menus are 320x200@70hz.

Yes, Epic Pinball has problems with the music in the menus (320x200@70Hz) when Vsync is ON and locked to 60Hz, there is no contradiction in what I've written.
For example, Mortal Kombat 3 is 320x240@60 in menu and 320x200@70 in game.

To me it seems that many DOS games internal speed relies on the GPU and Monitor sync timing and the game goes out of sync if the GPU is forced to other frequency.
I don't know, it maybe a DOSBox only related issue, and there is no way to force a GPU to a different refresh rate in real DOS to test it.

Lotus III has similar issues. Slowed music when you play with DVI 😀

PhilsComputerLab wrote:

Lotus III has similar issues. Slowed music when you play with DVI 😀

Real DOS? So the DVI is locked at 60Hz with Vsync and locks the GPU buffers at 60fps also, thus ruins the game timing.
If so, that proves that DOS games actually rely on the GPU timing, and that proves that 60Hz locked displays with vsync is very bad for dos gaming.

That means, if a DOS game (probably the GPU) calls for VSync and the monitor can only do 640/720x400 at 60Hz all hell breaks loose in DOS. 🤣
But there are some exceptions, like DOOM, everything is perfectly fine with Vsync locked at 60Hz even though the game is running 320x200@70.

Just to be clear here:
Do NOT force Vsync ON in nvidia CPL unless you have a G-Sync or CRT monitor that actually supports true 70Hz modes.
Forcing Vsync ON to 60Hz resolution like (Desktop) will break dos games timing in dosbox or real dos.

What we really want is a true 70Hz monitor, Vsync On, and dosbox to switch between modes automatically, Just like it was in good old Dos.
But currently only the premium priced Gsync/Freesync monitors and obsolete CRTs can do that.

James-F wrote:

What we really want is a true 70Hz monitor, Vsync On, and dosbox to switch between modes automatically.
Just like it was in good old Dos.

Again, G-Sync is pretty much the solution here. FreeSync might work too, but I haven't tried it personally.

Obviously not a solution for real DOS though, just DOSBox.

ZellSF wrote:

James-F wrote:

What we really want is a true 70Hz monitor, Vsync On, and dosbox to switch between modes automatically.
Just like it was in good old Dos.

Again, G-Sync is pretty much the solution here. FreeSync might work too, but I haven't tried it personally.
Obviously not a solution for real DOS though, just DOSBox.

I agree.
But if dosbox had two separate output resolutions for 70Hz and 60Hz modes that would include MANY other monitors at their native resolution! 😀
For example, any 144Hz IPS with any other GPU, not necessarily gsync or freesync, by creating custom resolution with 70Hz at native resolution.

For Dos it's either a CRT or an LCD (TN) with 70Hz... no IPS that I know of with VGA port that supports 70Hz.
Also the overclockable IPS panels from ebay are only Duallink DVI so I will not be able to connect that to my old Pentium machine.

James-F wrote:

Real DOS? So the DVI is locked at 60Hz with Vsync and locks the GPU buffers at 60fps also, thus ruins the game timing. If so, th […]
Show full quote

Real DOS? So the DVI is locked at 60Hz with Vsync and locks the GPU buffers at 60fps also, thus ruins the game timing.
If so, that proves that DOS games actually rely on the GPU timing, and that proves that 60Hz locked displays with vsync is very bad for dos gaming.

That means, if a DOS game (probably the GPU) calls for VSync and the monitor can only do 640/720x400 at 60Hz all hell breaks loose in DOS. 🤣
But there are some exceptions, like DOOM, everything is perfectly fine with Vsync locked at 60Hz even though the game is running 320x200@70.

Yup on a real DOS machine 😀

Connect screen with DVI and the game is slowed, connect with VGA and it's full speed.

Some games did indeed use the refresh for timing. There aren't many games though, I used to use DVI for a long time on my retro PC and I only read about Lotus III, after this I just used VGA.

how to check if my monitor supports real 70hz? I recently got a philips 19p4qyeb (ips) and it can correctly set itself to 1280x1024 70hz, even if a popup message says the recommended mode is 1280x1024 60hz.

vsynctester.com is a site where you can see what refresh rate your monitor is really using.

Myloch wrote:

how to check if my monitor supports real 70hz?

It depends if you want 720x400@70 or Native@70.
All monitors support 720x400@70 otherwise you will not be able to access your bios. 😊
The real question is whether the monitor support 70Hz without skipping frames!

You have to be a little tech savvy, but here we go:
Create a custom resolution with your GPU drives at your displays native resolution and 70Hz (use the auto settings), If the display accepted the resolution test, great, first step done.
Now enable this created custom resolution and select it as your desktop resolution, go to vsynctester.com to test if the display skips frames.
The image should be 70Hz smooth without skipped frames.

If you want to test 720x400@70, connect the display to your retro PC and run something like Supaplex (or any side scroller), it should be smooth without tearing or stuttering.

My Dell U2410 (IPS) does 720x400 and 640x400 at 70Hz but it skips frames because the panel itself is locked to 60Hz even though the display accepts 70Hz at that resolutions correctly.

ZellSF wrote:

jonnyjr wrote:

...
I'm curious about whether FreeSync/G-Sync will solve these problems or not, so I'm going to buy a FreeSync monitor and check it out in the near future.

G-Sync definitely does solve this problem. Unsure about FreeSync.

And yes, obviously the refresh rates are not exactly 60 or 70hz, but it's easier to type and no one's getting confused.

I've now got a FreeSync monitor, and it seems to work fine without stuttering when the game actually outputs more frames per second than the low limit of the FreeSync range (48 Hz on my monitor). That means this works OK for games like Tyrian and Jazz Jack Rabbit, but not for games like Raptor: Call of the Shadows and Commander Keen (I believe those games outputs 35 frames per second(?)).

Some fhd IPS unofficially support up to 72 Hz in native resolution.
The example is Asus mx259h, which unfortunally does not work (need special settings?) at 70 Hz, but 71 Hz works.

You need to create custom resolution in video driver's settings to set unofficial refresh rate.

If you have IPS and photocamera, you may test is there frame skipping
http://www.testufo.com/#test=frameskipping

James-F wrote:

If you have a CRT the absolutely best settings for dosbox to behave like real dos would:
output=opengl

only output=surface shows original image on CRT, while any other makes it blurry

James-F wrote:

My Dell U2410 (IPS) does 720x400 and 640x400 at 70Hz but it skips frames because the panel itself is locked to 60Hz even though the display accepts 70Hz at that resolutions correctly.

The 2209WA can supposedly be 'overclocked' to up to 75Hz without dropping frames. I wonder if the U2410 can too. Probably not, though.

I recently picked up the ASUS PB277Q monitor and will probably be returning it because what I presume to be the coating makes it look like someone smeared grease underneath the LCD. However I'd like to share a few notes about it first. It is not an IPS Panel but the 28Q is.

2560x1440 @ 75hz 1ms (although the Vsync tester page shows much more than 1ms)
TN Panel
VGA, HDMI, DVI and DP connectivity
Resolution through VGA caps out at 1080p meaning you need DVI, DP or HDMI to use 1600x1200 resolution.
Has "IBM Modes" of 640x350 and 720x400 @ 70hz listed as supported in the manual but I needed to create a custom resolution to actually use 720x400 in DOSBox.
Has 4:3 and 1:1 aspect ratio controls but 1:1 will just yield a tiny image and 4:3 can only be activated when you're using a 4:3 resolution... so I can't force 720x400 into 4:3 which is what I'm assuming was done with CRT monitors or 640x400 since they are not 4:3 resolutions.

Very, very confusing stuff trying to get the most accurate/real resolutions on an LCD in DOS or Dosbox.