What LCD/LED monitors are not able to do this?

cyclone3d wrote on 2023-05-07, 02:56:

What LCD/LED monitors are not able to do this?

Actually many. Most I have tested don't support DOS native resolution (720x400). You end up with a stretched image. It's ok for a short time usage, but a correctly proportioned image is so much better.

This is one such monitor just to give you an example: LG 24MK430H-B. It supports 640x480, but not 720x400 at a correct aspect ratio.

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you wanted within hardware capability limits
- http://www.geocities.ws/podernixie/htpc/misc/dos-en.html
- https://www.qsl.net/dh1dm/tv_50hz_svga/

in windows you can use
- powerstrip https://www.audioholics.com/diy-audio/powerst … e-a-user-manual
- Custom Resolution Utility (CRU)
- nvidia panel
etc

This has everything to do with the board driving the display (the board in the monitor itself).

So technically that monitor has that ability, but not at all resolutions, which is a different issue than the feature being completely absent.

On good monitors they at least have the option to letterbox the input so th monitor runs at a higher resolution and the input is put in the middle of that.

rasz_pl wrote on 2023-05-07, 03:19:

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you […]
Show full quote

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you wanted within hardware capability limits
- http://www.geocities.ws/podernixie/htpc/misc/dos-en.html
- https://www.qsl.net/dh1dm/tv_50hz_svga/

in windows you can use
- powerstrip https://www.audioholics.com/diy-audio/powerst … e-a-user-manual
- Custom Resolution Utility (CRU)
- nvidia panel
etc

Quite interesting, great resources. Thanks. Some day I may create an adapter and use the VGA output.

This thread is about GPUs with DVI output that automatically resize DOS (720x400) output to 4:3 on a modern display.

tauro wrote on 2023-05-07, 03:30:

rasz_pl wrote on 2023-05-07, 03:19:

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you […]
Show full quote

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you wanted within hardware capability limits
- http://www.geocities.ws/podernixie/htpc/misc/dos-en.html
- https://www.qsl.net/dh1dm/tv_50hz_svga/

in windows you can use
- powerstrip https://www.audioholics.com/diy-audio/powerst … e-a-user-manual
- Custom Resolution Utility (CRU)
- nvidia panel
etc

Quite interesting, great resources. Thanks. Some day I may create an adapter and use the VGA output.

This thread is about GPUs with DVI output that automatically resize DOS (720x400) output to 4:3 on a modern display.

DVI doesnt matter here, it encapsulates same timing signals as in VGA. This is why manipulating timings using Custom Resolution Utility (CRU) / nvidia panel doesnt discriminate between output methods.
Of course modern GPUs are black boxes and you wont be able to reprogram output from a DOS session, but running DOS inside windows should let you define your own video modes.

rasz_pl wrote on 2023-05-07, 05:00:

tauro wrote on 2023-05-07, 03:30:

rasz_pl wrote on 2023-05-07, 03:19:

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you […]
Show full quote

this strikes me as purely software issue/limitation. Back in ISA SVGA days you could directly reprogram CRTC for any timings you wanted within hardware capability limits
- http://www.geocities.ws/podernixie/htpc/misc/dos-en.html
- https://www.qsl.net/dh1dm/tv_50hz_svga/

in windows you can use
- powerstrip https://www.audioholics.com/diy-audio/powerst … e-a-user-manual
- Custom Resolution Utility (CRU)
- nvidia panel
etc

Quite interesting, great resources. Thanks. Some day I may create an adapter and use the VGA output.

This thread is about GPUs with DVI output that automatically resize DOS (720x400) output to 4:3 on a modern display.

DVI doesnt matter here, it encapsulates same timing signals as in VGA. This is why manipulating timings using Custom Resolution Utility (CRU) / nvidia panel doesnt discriminate between output methods.
Of course modern GPUs are black boxes and you wont be able to reprogram output from a DOS session, but running DOS inside windows should let you define your own video modes.

While theoretically you are correct and your technical knowledge is certainly important, let me state again that I'm interested in AGP cards that automatically resize their pure DOS output to 4:3 for the kind of monitors that don't do it automatically which are in my experience, most.

Have you ever come across such card/monitor combination? I'd be interested to hear about people's practical experiences.

In my case, the aforementioned 9200SE does send the right signals i.e. resizes its output only through DVI output. VGA output works, but most monitors I've tried don't display the correct aspect ratio.

I opened this thread to hear from other people that know about such cards to share information and create a knowledge base.

Please stay on topic.

If I remember correctly, old Radeon cards do not resize to 4:3, they resize it to 5:4 aspect ratio for some odd reason.

The Serpent Rider wrote on 2023-05-07, 05:38:

If I remember correctly, old Radeon cards do not resize to 4:3, they resize it to 5:4 aspect ratio for some odd reason.

You prompted me to do some measurements and take some notes.

It turns out that the DOS video signal is upscaled and resized to 1024x768@60Hz, that's what's displayed in the monitor's settings/status.
I measured the screen and the aspect ratio is a perfect 4:3.

It'd be very interesting to know what cards actually do resize to 5:4 and what cards resize to 4:3 and which ones have the best DOS compatibility in terms of less scrolling defects.

If I remember correctly, some of these older cards only output 60 Hz over DVI. This can lead to some weird timing issues with certain DOS games.

In particular, I think the original Tyrian (version 1.1) slows down the entire game (including the music) when played that way. I guess some DOS games which run at 320x200 expect a 70 Hz refresh rate and sync to it.

tauro wrote on 2023-05-07, 05:18:

Please stay on topic.

what Im trying to communicate is its not hard GPU vendor/model dependent, but a software issue that might work differently on different brands of card with same chip merely as a whim of whoever(and when, early on nobody needed any scaling) was compiling bios for specific card model.
in case of older R200 radeons we at least have access to documentation (including CRTC ) and sources for a working driver https://github.com/RAOF/xf86-video-ati/blob/m … radeon_driver.c https://android.googlesource.com/kernel/goldf … gacy_crtc.c#546 so someone persistent enough could figure out how to force whatever timing/scaling he desires in pure dos

Main problem with 720x400 is that you have to actively force it to be 4:3, since by it's own pixel ratio - it's detected as ~16:9 resolution by LCD panels. Forcing aspect ratios isn't usually implemented at vBIOS/DOS level (requires Windows drivers).

Aside from above, and as mentioned previously, 720x400 by default has 70Hz refresh.
In 99% of the cases for scaling on DVI-D/HDMI out, you will get limited to 60Hz.

There has been an interesting development.

For a long time I had an unbranded FX5500 that doesn't do auto-resizing through DVI. But I have recently come across one that does! It's an MSI 8911 Ver 3.30.

I wasn't aware that the same model of video card could do DVI auto-resizing depending on its manufacturer. Both are 128-bit FX5500, but the MSI has 256MB, while the other one 128MB.

This opens a new question, could the BIOS be the determining factor or... what is it? What would a mod to force auto-resizing through DVI entail? What needs to be swapped or it's impossible? Just for curiosity.

Joseph_Joestar wrote on 2023-05-07, 08:04:

If I remember correctly, some of these older cards only output 60 Hz over DVI. This can lead to some weird timing issues with certain DOS games.

In particular, I think the original Tyrian (version 1.1) slows down the entire game (including the music) when played that way. I guess some DOS games which run at 320x200 expect a 70 Hz refresh rate and sync to it.

Could please give a me a list of some games to test? The only one I have had problems with is Commander Keen.

the geforce 8600gt resizes to 4:3 in dos when connected to dvi, but also this depends which aspect ratio I set on the monitor, in my Acer monitor kG271 244hz I must set wide mode to aspect otherwise the image end up stretched

tauro wrote on 2023-07-22, 19:24:

Could please give a me a list of some games to test? The only one I have had problems with is Commander Keen.

As mentioned above, Tyrian version 1.1 is one game where I've personally experienced this behavior.

However, after noticing that, I stopped using DVI for DOS gaming entirely. So, that's the only example I have.

After doing some testing, I can confirm that the display refresh rate is tied to the overall game speed in some games.

All cards that auto-resize to 4:3 through DVI that I could test do so at 1280x1024, and these are their respective refresh rates:

A9200SE 75Hz (ASUS)
R9250 75Hz (GIGABYTE)
FX5500 60Hz (MSI)
FX5200 60Hz (XFX)

To summarize, so far
ATI = 75Hz
NVIDIA = 60Hz

The only AGP card that I have that doesn't auto-resize to 4:3 through DVI (FORSA FX5500) outputs 1920x1080 at 60Hz, that is 16% slower than what it should be (720x400@70Hz for most DOS things).

I only tested a very limited set of games, but I noticed that some are affected by the refresh rate, while others are not or very little.
Those that are affected play/sound either 7% faster (75Hz) or 16% slower (60Hz) than what they should.

Games that are affected by the display refresh rate:
Tyrian
Lotus III

Games whose speed is not affected by the display frame rate:
Prince of Persia 2
Alone in the Dark
Leisure Suit Larry 1 (VGA)
GODS
Prehistorik 2
Pinball Dreams 2

I couldn't say whether there are problems when playing Tyrian at 60Hz, but I noticed problems when playing Alone in the Dark at 75Hz.

Using an ATI card (75Hz), playing Alone in the Dark, even if the speed of the game/music is correct, sometimes the PCM sounds don't play, they are skipped (in the intro, when the woman gets out of the car you can't hear the steps). To fix this, with TweakBIOS 1.53c, I disabled ISA I/O recovery and that sound now plays and presumably everything works as expected.

So far, considering the display refresh rate sensitive games, the ATI cards seem to be better (only 7% faster vs. 16% slower for the NVIDIA cards).

I'm still thinking, how could we force the cards to output 70Hz instead of 75 or 60? Could it be done? Who chose those refresh rates and if they would resize their output to 4:3 through DVI or force 16:9? and why?

Is there any card out there that outputs 70Hz through DVI and resizes to 4:3?

Other notes:
The NVIDIA cards give a blurrier image, some sort of interpolation, while the ATI cards don't, they have a sharper image.
Commander Keen 4 has the scrolling bug with the ATI cards, while the NVIDIA cards scroll smoothly.

tauro wrote on 2023-07-26, 02:41:

Other notes:
The NVIDIA cards give a blurrier image, some sort of interpolation, while the ATI cards don't, they have a sharper image.
Commander Keen 4 has the scrolling bug with the ATI cards, while the NVIDIA cards scroll smoothly.

The DVI blurring at non-native resolutions is a known Nvidia problem. It applies to Windows games as well.

For example, if you're playing a game that only runs at a fixed resolution (e.g. StarCraft in 640x480) on a 1280x1024 monitor using DVI, it will look very blurry on Nvidia cards. In such cases, you will generally get better and less blurry results using VGA on that same card and monitor setup.

Personally, I only recommend using DVI on Nvidia cards when playing games at the monitor's native resolution, or something close to that with scaling disabled in the driver. Quake 2 is a good candidate for the latter, since it only supports 1280x960 and not 1280x1024. Set the scaling to either "Centered Output" or "Fixed Aspect Ratio" in the Nvidia driver panel, and it will look razor sharp on a 1280x1024 monitor.

320x200 isn't 4:3, it's 16:10. If you integer scale it, you end up with stretched image. I have not to found a solution which would scale it "circle perfect" to modern displays.