DOS games are 72 Hz I believe.

Most LCDs support this fine. It's not hard to test, just get a game that has super smooth scrolling and see if it work. Also use the OSD and it will display the refresh rate.

If you use DVI for example there are games that will have issues with music slowing down because the game syncs to the refresh rate.

In general I would say that newer monitors might have issues with DOS resolutions because nobody cares about it.

In general ALL LCDs support higher refresh rates at lower non-native resolutions! Many even at native resolutions. Many can do 75Hz at Full HD but need software tricks to enable this.

VGA cards use 70 Hz for the usual modes.
early SVGA cards stick to the 8514/A standard and have like 56 Hz at 800x600x16 and 43 Hz interlaced at 1024.
later SVGA use typically 60 Hz, but may have a refresh rate tool or VBE3 support.
Some demos use even more customized modes.

Mau1wurf1977 wrote:

In general I would say that newer monitors might have issues with DOS resolutions because nobody cares about it.

In general ALL LCDs support higher refresh rates at lower non-native resolutions! Many even at native resolutions. Many can do 75Hz at Full HD but need software tricks to enable this.

I bet the said software does not run on pure DOS. So, can the software set the LCD's refresh rate permanently (you set it once and it stays until you set it again), or does the software need to run in the background while the application (DOS game) is running?

elianda wrote:

later SVGA use typically 60 Hz, but may have a refresh rate tool or VBE3 support.
Some demos use even more customized modes.

Does such refresh rate tool work with modern LCD/LED monitors? For example, does SDD work with modern monitors?

This monitor isn't even real 240 Hz. It uses a 120 Hz input and converts it to 240 Hz. It's like saying 6-bit+FRC/dithering is 8-bit color depth 🙄

I wouldn't bet on such monitors becoming cheap anytime soon. But you can already get affordable 120 Hz monitors if image quality doesn't bother you.

d1stortion wrote:

This monitor isn't even real 240 Hz. It uses a 120 Hz input and converts it to 240 Hz. It's like saying 6-bit+FRC/dithering is 8-bit color depth 🙄

Well I think it doesn't quite matter if it can support or up-convert myriads of native DOS refresh rates, or does it?

Setting the Refresh rate changes the output of the graphics card, so it is independent of the monitor. However to get a screen output the monitor has to follow the signal.

Kreshna Aryaguna Nurzaman wrote:

I bet the said software does not run on pure DOS. So, can the software set the LCD's refresh rate permanently (you set it once and it stays until you set it again), or does the software need to run in the background while the application (DOS game) is running?

Sorry I didn't explain it well.

That software is needed to trick the video driver / Windows in believing the LCD supports a higher refresh rate like 75Hz. It's similar to setting a custom resolution but permanently.

The monitor tries to display whatever comes down the VGA cable. If it can't handle it you will get a "signal out of range" message.

Mau1wurf1977 wrote:

Sorry I didn't explain it well. […]
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Kreshna Aryaguna Nurzaman wrote:

I bet the said software does not run on pure DOS. So, can the software set the LCD's refresh rate permanently (you set it once and it stays until you set it again), or does the software need to run in the background while the application (DOS game) is running?

Sorry I didn't explain it well.

That software is needed to trick the video driver / Windows in believing the LCD supports a higher refresh rate like 75Hz. It's similar to setting a custom resolution but permanently.

The monitor tries to display whatever comes down the VGA cable. If it can't handle it you will get a "signal out of range" message.

I see. How do we know a monitor can handle a particular refresh rate, then? If a monitor can handle 120 Hz, can it also handle lower (but more esoteric) refresh rate like 56 Hz or 43 Hz?

It should but there is only one way of really knowing: testing 😀

Well it is most likely the same thing as with TVs. They have something like 600 Hz panels. There is no video source capable of this, and many displays support standard 50 and 60 Hz formats over whatever cables. The panel just displays one image 10 times to make it flicker less, and can even do some light video processing, like noise removal or it might even try to create intermediate 600Hz frames between two incoming 60Hz frames so that moving stuff looks smoother. The trick is that when the panel supports this fast rates, the display can show 3D stereo images so that both eyes still get 60Hz rate natively, and even one eye can get one frame five times and other eye five times. And with modern technologies, the liquid crystals are faster to settle to new value, meaning the 10%-90% settling time (response time) is faster so the panels can might as well offer the improved refresh rate as well.

Anyway, two most likely refresh rates used by DOS games are 70Hz and 60Hz. All 400 line modes such as text mode and 320x200 use 70Hz, and all 480 line modes (320x240, 640x350 and 640x480) use 60Hz. Unless programs create custom modes that is.

Monitor resolution support can be found on the manual, many modern monitors say they do not support 70Hz modes. Usually manuals are downloadable as PDF from the manufacturer.

Mau1wurf1977 wrote:

It should but there is only one way of really knowing: testing 😀

Unfortunately, most computer stores in the country I love do not have return policy at all - and I found it quite cumbersome to carry my pure DOS system to the computer store. 🙁

Well, specs for certain models can be found on the internet, but I wonder if a monitor can support a refresh rate not listed on its specs. Let say, a monitor is capable to support 70 Hz atau 120 Hz. But can it support, say, 43 Hz?

Jepael wrote:

Well it is most likely the same thing as with TVs. They have something like 600 Hz panels. There is no video source capable of this, and many displays support standard 50 and 60 Hz formats over whatever cables. The panel just displays one image 10 times to make it flicker less, and can even do some light video processing, like noise removal or it might even try to create intermediate 600Hz frames between two incoming 60Hz frames so that moving stuff looks smoother.

Hm. So can it be said, that a monitor can generally support lower refresh rate than what's written on its specs?

Yes that's right.

I'm certain that any LCD will display a picture, but things like:

- Scaling quality
- Aspect ratio
- 60 or 70 Hz

Are things that are hard to predict.

I would go for second hand 17" or 19" screens. They aren't that old to have issues with ghosting and should still offer good DOS compatibility.

Many screens have 4:3 mode buttons, but often they only work for DVI and not for VGA.

Maybe we should start a thread with members testing their screens and reporting on DOS compatibility. We would have to come up with a few criteria and tests though so that there is a standard.

Actually it is not the refresh rate that limits the display but the supported Horizontal Frequency range and Pixel Clock plus some constraints due to Input signal conversion logic.
So if you calculate the corresponding frequencies from resolution and vertical refresh and they are in the supported ranges, then it is likely that the monitor shows this mode.

Mau1wurf1977 wrote:

Maybe we should start a thread with members testing their screens and reporting on DOS compatibility. We would have to come up with a few criteria and tests though so that there is a standard.

Hmm, how about this thread?

elianda wrote:

Actually it is not the refresh rate that limits the display but the supported Horizontal Frequency range and Pixel Clock plus some constraints due to Input signal conversion logic.
So if you calculate the corresponding frequencies from resolution and vertical refresh and they are in the supported ranges, then it is likely that the monitor shows this mode.

What is the equation? I'd like to see examples, so that I can calculate it based on the known specs of the monitor. Thanks, by the way.

Mau1wurf1977 wrote:

Maybe we should start a thread with members testing their screens and reporting on DOS compatibility.

Like this one? 😉

This: http://wiki.osdev.org/Video_Signals_And_Timing
shows a nice timing overview and gives formula examples using GTF.

d1stortion wrote:

Mau1wurf1977 wrote:

Maybe we should start a thread with members testing their screens and reporting on DOS compatibility.

Like this one? 😉

Yea 😀

So, anyone wants to put their result?

elianda wrote:

This: http://wiki.osdev.org/Video_Signals_And_Timing
shows a nice timing overview and gives formula examples using GTF.

Interesting, thanks!