digger wrote on 2024-11-28, 10:27:

Didn't such advanced EGA cards also use PWM to support 64 colors on CGA monitors as well?

In theory they could simulate more colours, but I don't have an EGA card at hand right now. 🙁

The ATI Small Wonder has the ability to simulate shades on gray on an Hercules/MDA monitor, for example. To display CGA in 320x200 4c.
It makes use of the intensity pin at one point, though.

digger wrote on 2024-11-28, 10:29:

Another question: how well do those DOS TSRs that force 15kHz mode work with more modern VGA cards and chipsets?

Has anybody tried those TSRs on more recent hardware, by any chance?

Hi, normal VGA stuff works fine on the custom cable with a DOS TSR. 🙂

Mode 13h (320x200 256c) and mode 12h (640x480 16c) work just fine with generic VGA cards, including modern AGP and PCIe cards.
The CGA/EGA modes in 320x200 and 640x200 are no problem, either.

Special chipset support is required for the odd, "tweaked" modes and higher resolutions (past 640x480 16c).
That's when the TSR needs to be able to understand how the chips' enhanced CRTC works internally, to make the correct adjustments.
Because that's when things go beyond IBM's original VGA implementation.

That's when you need to have one of the supported SVGA cards/chips from back in the day.
The TSR normally explains this in the supplied readme file.

Edit: Some of these TSRs originally were meant for use in arcade cabs, I think.
Back in the 90s, people built/rebuilt arcade cabinets and then installed a PC mainboard running DOS and an DOS-based emulator (MESS, MAME etc).

These PCs were Pentium IIs class and higher, often, rather than vintage PCs.
The idea was to leave the original 15 KHz CRT monitor in place and connect it to PC graphics card directly, for authentic and flicker free graphics.
So that resolutions like 320x200 or 320x240 had looked same as with the original arcade board.

The DOS environment had the advantage that it was very fast, low latency and that the VGA CRTC could be configured for all kinds of timings.
- Same thing was not so easy to do on Windows at the time.
Also, the emulation scene was strong on DOS, still. DOS provided best performance here, too. And it was fine for embedded use, anyway.

Often, the buttons and joysticks on the arcade cab had been rewired to a special PC interface, too.
Either attached to gameport or parallel port or to a hacked keyboard.
Speaking under correction, though.

Jo22 wrote on 2024-11-28, 10:27:

To be honest, I didn't notice a visual difference between RGB and Composite. But this was a SCART TV with a PAL decoder. […]
Show full quote

boggit wrote on 2024-11-28, 09:45:

Has anyone here tried using an AverKey solution to run VGA on an RGB monitor? How good was the quality?

To be honest, I didn't notice a visual difference between RGB and Composite.
But this was a SCART TV with a PAL decoder.

The screenshots can be seen here: Re: MCGA Games (PC/DOS) - LCD vs CRT
I've used SCART @60 Hz mainly, but PAL 60 through Composite didn't look any different to me.
This monitor's CRT screen mask was too blurry/low-res for it to be visually noticeable.

(Quick explanation. I've configured an 60 Hz output on the converter box because common VGA resolution is 640x480 60 Hz which is close to American TV standard;
if I would use 50 Hz the picture would be squashed/letterboxed due to European TV standard being of higher resolution - ca. 720x576 50 Hz.
Video game consoles like NES or Sega Genesis have similar problems with PAL borders.
On an analogue video monitor such as an Commodore 1702 things can be compensated by using h-size and v-size knobs. On an ordinary SCART TV, this option doesn'texist sadly.)

For NTSC users with an RGB-capable video monitor the result might be different.
NTSC via Composite can has a lot of colour bleed, artifacts and rainbow banding effects, making RGB a better choice.

Thank you!

That actually doesn't look half bad. Which specific AverMedia device did you use for this?

And all the CRT screenshots is from you going VGA card -> AverMedia device -> Composite cable -> CRT?

I bought one of these, complete with VGA->SCART cable, off eBay.

Do y'all figure it would work, then, to hook up a 286 with a VGA card -> AverKey Pro3 -> VGA-to-SCART cable -> this SCART-to-RGB cable* -> My (PAL) Commodore 1084s-P2 monitor?

* Works great for original hardware SNES gaming when combined with a SNES multiout-> SCART. Really crisp image!

digger wrote on 2024-11-28, 10:29:

Another question: how well do those DOS TSRs that force 15kHz mode work with more modern VGA cards and chipsets?

Has anybody tried those TSRs on more recent hardware, by any chance?

I've used VGATV on:
Matrox Millenium and Mystique (PCI): 256c only
Generic FX5200 (AGP): 256c only
Radeon 9700 Pro (AGP): 256c only
S3 Virge (PCI): both 16c and 256c modes work properly

Not exactly modern by any stretch, but newer than the usual ISA/VLB cards one would usually use it on

digger wrote on 2024-11-28, 10:27:

Jo22 wrote on 2024-11-28, 09:31:

I don’t know of any EGA/VGA card which does use interlacing on an EGA monitor to support higher resolutions. It was rather oppos […]
Show full quote

I don’t know of any EGA/VGA card which does use interlacing on an EGA monitor to support higher resolutions.
It was rather opposite. Limited, flickering EGA support on CGA monitors (to simulate 640x350 16c by using itnerlacing).

PS: A true EGA monitor can display 64 colours via digital TTL port. However, EGA doesn't have a dedicated 64c mode.
It rather has several fixed palettes and can display 16c at once only.
Some games like that Iron Man racing game or that Snoopy game do use 64 colour mode.
They switch palettes on the fly, as needed, as far as I understand.

Didn't such advanced EGA cards also use PWM to support 64 colors on CGA monitors as well?

This is something that always perplexed me as PWM / dithering/ frame-field schemes to make more “colors “ was done way back in the 70’s

The cards in question On monochrome they did a little magic for 4 color and even in a few cases “16 color” emulation
but I am not aware of any of the advanced pseudo EGA/VGA 8/16 hybrid cards that truly brought newer standards backwards to older color monitors.

AKA Generally you got just the traditional 16 CGA colors on a CGA monitor, no PWM, no special modes. 15khz RGB Analog screens supported the full 256,000 color vga pallet but again not aware of any hybrid card that took advantage of it.

rmay635703 wrote on 2024-11-29, 03:01:

This is something that always perplexed me as PWM / dithering/ frame-field schemes to make more “colors “ was done way back in t […]
Show full quote

digger wrote on 2024-11-28, 10:27:

Jo22 wrote on 2024-11-28, 09:31:

I don’t know of any EGA/VGA card which does use interlacing on an EGA monitor to support higher resolutions. It was rather oppos […]
Show full quote

I don’t know of any EGA/VGA card which does use interlacing on an EGA monitor to support higher resolutions.
It was rather opposite. Limited, flickering EGA support on CGA monitors (to simulate 640x350 16c by using itnerlacing).

PS: A true EGA monitor can display 64 colours via digital TTL port. However, EGA doesn't have a dedicated 64c mode.
It rather has several fixed palettes and can display 16c at once only.
Some games like that Iron Man racing game or that Snoopy game do use 64 colour mode.
They switch palettes on the fly, as needed, as far as I understand.

Didn't such advanced EGA cards also use PWM to support 64 colors on CGA monitors as well?

This is something that always perplexed me as PWM / dithering/ frame-field schemes to make more “colors “ was done way back in the 70’s

The cards in question On monochrome they did a little magic for 4 color and even in a few cases “16 color” emulation
but I am not aware of any of the advanced pseudo EGA/VGA 8/16 hybrid cards that truly brought newer standards backwards to older color monitors.

AKA Generally you got just the traditional 16 CGA colors on a CGA monitor, no PWM, no special modes. 15khz RGB Analog screens supported the full 256,000 color vga pallet but again not aware of any hybrid card that took advantage of it.

Hi, indeed. I think it was a matter about practibility in real life, also.

The EGA Wonder 800 could do full EGA on an Hercules and CGA monitor, but the image was very flickery.

It was fine for playing a poker game or a golf sim or for testing purposes, but not for hours of work in the office.
The eye strain and headache wasn't worth it. 🙁

Except when having the IBM 5151 MDA monitor, which had an extra ordinary slow after glow so flickering disappeared when simulating colours.

To those users, the EGA Wonder 800 did same thing as the ATI Small Wonder did before.

It did allow using the existing, widespread monochrome office monitors for various modern applications.
And that alone was worth it to many users, I suppose.

My dad included, who had still used such an MDA monitor in 1989 in the office.

More information about EGA Wonder (not affiliated):
https://dosdays.co.uk/topics/Manufacturers/at … _wonder_800.php

The add below says "[..] EGA, CGA, MDA on MultiSync, EGA [..] RGB, TTL Monochrome and [..] monitors"
And that's it, pretty much. Ordinary composite out in 15 KHz is supported for 200 line modes only, in monochrome.

The full EGA resolution with 350 lines is possible only via internal monitor of the Compaq Portable luggable computer. Or a very tolerant video monitor.
The Compaq monitor was not an ordinary composite monitor, it can do sync to about 18 KHz in addition to 15 KHz.

Edit: More information on the internal Compaq monitor (not affilated):
https://forum.vcfed.org/index.php?threads/ega … rtable-1.51290/

That's why the image isn't always being stable in this YouTube video here, I suppose:
https://www.youtube.com/watch?v=KsY635VdOQk&t=2167s

That being said, full EGA (&HGC+MDA) seems to be possible on MDA monitors (about same resolution as full EGA) and CGA monitors (by pushing the specs, using interlacing).

Edit: Correction. If I do understand the advertisement correctly, then normal 15 KHz composite monitors may be supported via interlacing, too.
By contrast, the non-interlaced composite output likely needs an 18 KHz capable monitor, though.
That's a sync rate what MDA monitors do use, to master 350 lines without interlacing.

Edit: For sake of curiosity, yes, it's possible to drive an ordinary video monitor from a Hercules card. 😃
The monitor needs some slight modification, though.

More info here (not affilated): http://boginjr.com/electronics/rad/rgbi/
https://boginjr.com/electronics/old/tesla-pmd60/

Edit: Sorry for the many mistakes/edits. It's night here and I'm very sleepy. 😴

Jo22 wrote on 2024-11-29, 04:15:

Hi, indeed. I think it was a matter about practibility in real life, also. […]
Show full quote

rmay635703 wrote on 2024-11-29, 03:01:

This is something that always perplexed me as PWM / dithering/ frame-field schemes to make more “colors “ was done way back in t […]
Show full quote

digger wrote on 2024-11-28, 10:27:

Didn't such advanced EGA cards also use PWM to support 64 colors on CGA monitors as well?

This is something that always perplexed me as PWM / dithering/ frame-field schemes to make more “colors “ was done way back in the 70’s

The cards in question On monochrome they did a little magic for 4 color and even in a few cases “16 color” emulation
but I am not aware of any of the advanced pseudo EGA/VGA 8/16 hybrid cards that truly brought newer standards backwards to older color monitors.

AKA Generally you got just the traditional 16 CGA colors on a CGA monitor, no PWM, no special modes. 15khz RGB Analog screens supported the full 256,000 color vga pallet but again not aware of any hybrid card that took advantage of it.

Hi, indeed. I think it was a matter about practibility in real life, also.

The EGA Wonder 800 could do full EGA on an Hercules and CGA monitor, but the image was very flickery.

It was fine for playing a poker game or a golf sim or for testing purposes, but not for hours of work in the office.
The eye strain and headache wasn't worth it. 🙁

Except when having the IBM 5151 MDA monitor, which had an extra ordinary slow after glow so flickering disappeared when simulating colours.

To those users, the EGA Wonder 800 did same thing as the ATI Small Wonder did before.

It did allow using the existing, widespread monochrome office monitors for various modern applications.
And that alone was worth it to many users, I suppose.

My dad included, who had still used such an MDA monitor in 1989 in the office.

The attachment MDA89.jpg is no longer available

More information about EGA Wonder (not affiliated):
https://dosdays.co.uk/topics/Manufacturers/at … _wonder_800.php

The add below says "[..] EGA, CGA, MDA on MultiSync, EGA [..] RGB, TTL Monochrome and [..] monitors"
And that's it, pretty much. Ordinary composite out in 15 KHz is supported for 200 line modes only, in monochrome.

The full EGA resolution with 350 lines is possible only via internal monitor of the Compaq Portable luggable computer. Or a very tolerant video monitor.
The Compaq monitor was not an ordinary composite monitor, it can do sync to about 18 KHz in addition to 15 KHz.

That's why the image isn't always being stable in this YouTube video here, I suppose:
https://www.youtube.com/watch?v=KsY635VdOQk&t=2167s

That being said, full EGA (&HGC+MDA) seems to be possible on MDA monitors (about same resolution as full EGA) and CGA monitors (by pushing the specs, using interlacing).

Edit: Correction. If I do understand the advertisement correctly, then normal 15 KHz composite monitors may be supported via interlacing, too.
By contrast, the non-interlaced composite output likely needs an 18 KHz capable monitor, though.
That's a sync rate what MDA monitors do use, to master 350 lines without interlacing.

Edit: For sake of curiosity, yes, it's possible to drive an ordinary video monitor from a Hercules card. 😃
The monitor needs some slight modification, though.

More info here (not affilated): http://boginjr.com/electronics/rad/rgbi/
https://boginjr.com/electronics/old/tesla-pmd60/

Edit: Sorry for the many mistakes/edits. It's night here and I'm very sleepy. 😴

I actually have an EGA Wonder 800+ card that I currently use as my main graphics card on my retro build. Really good card!

Jo22, did you see my post above, about the setup I have in mind with the AverKey?

boggit wrote on 2024-11-29, 08:18:

I actually have an EGA Wonder 800+ card that I currently use as my main graphics card on my retro build. Really good card!

That's cool! 🙂👍

boggit wrote on 2024-11-29, 08:18:

Jo22, did you see my post above, about the setup I have in mind with the AverKey?

Hi, yes, I did.

I wanted to take a few photos, sorry for late reply! 😅

In the picture thread, I've used another converter, a TV-View Pocket (as seen on page 2).
Re: MCGA Games (PC/DOS) - LCD vs CRT

I've used it via SCART/RGB most of the time when taking the screenshots,
but when I switched cables (and changed DIP switches accordingly) the image via PAL/Composite wasn't really different on the monitor (SCART TV).

_
The AVerKey Pro converter I've used for my YouTube videos wasn't worse by any means.
It's a good model, the other AVerKeys should be comparable, though.
It can be seen in action here, for example. CRT was connected via yellow composite cable and a SCART adapter plug:

Copper demo on big CRT TV
https://www.youtube.com/watch?v=1xXTF4et1sE

SkyRoads intro on big CRT monitor (TV set)
https://www.youtube.com/watch?v=4w22Yuy2bcY

Loonies 8192 on a 16MHz 286 PC
https://www.youtube.com/watch?v=VZMme7Edx6s

Copper demo by Surprise (286, CRT TV)
https://www.youtube.com/watch?v=NcyDC2mGQa4

Edit: I think that's ok. That being said, the alternative via VGATV as mentioned by maxtherabbit remains an option.
What comes to mind is that the monochrome variant of the 15 KHz VGA cable can be built quite easily, I think.
So users with a green or amber video monitor can 'upgrade' to a VGA card quite easily here.
- I'm thinking of PC/XT owners with a CGA card and a mono monitor connected via RCA plug (not too uncommon back then).

Jo22 wrote on 2024-11-29, 13:49:

Hi, yes, I did.

I wanted to take a few photos, sorry for late reply! 😅

No worries! Thanks for getting back to me!

Jo22 wrote on 2024-11-29, 13:49:

In the picture thread, I've used another converter, a TV-View Pocket (as seen on page 2). Re: MCGA Games (PC/DOS) - LCD vs CRT […]
Show full quote

In the picture thread, I've used another converter, a TV-View Pocket (as seen on page 2).
Re: MCGA Games (PC/DOS) - LCD vs CRT

I've used it via SCART/RGB most of the time when taking the screenshots,
but when I switched cables (and changed DIP switches accordingly) the image via PAL/Composite wasn't really different on the monitor (SCART TV).

Ok, good to know! Maybe the RGB SCART cable was unnecessary then, but doesn't hurt to have that option. If the SCART RGB option won't work (for example if the AverKey device won't lower that output from 31.5khz to 15khz) then I can use the S-VIDEO ports instead, or just composite.

Jo22 wrote on 2024-11-29, 13:49:

The AVerKey Pro converter I've used for my YouTube videos wasn't worse by any means. It's a good model, the other AVerKeys shoul […]
Show full quote

The AVerKey Pro converter I've used for my YouTube videos wasn't worse by any means.
It's a good model, the other AVerKeys should be comparable, though.
It can be seen in action here, for example. CRT was connected via yellow composite cable and a SCART adapter plug:

Copper demo on big CRT TV
https://www.youtube.com/watch?v=1xXTF4et1sE

SkyRoads intro on big CRT monitor (TV set)
https://www.youtube.com/watch?v=4w22Yuy2bcY

Loonies 8192 on a 16MHz 286 PC
https://www.youtube.com/watch?v=VZMme7Edx6s

Copper demo by Surprise (286, CRT TV)
https://www.youtube.com/watch?v=NcyDC2mGQa4

Great! Why both composite and SCART though? At the same time?

Jo22 wrote on 2024-11-29, 13:49:

Edit: I think that's ok. That being said, the alternative via VGATV as mentioned by maxtherabbit remains an option.

Yeah definitely, though I would need to make my own cable for that, and I don't have the skillset or the energy to do so.

Ok so what about this solution

BitWrangler wrote on 2024-11-25, 21:11:

What VGA cards are you using? If it's Trident, Cirrus Logic and a couple of others, you can change the output to 15khz in DOS with a TSR. Then all you have to do is make a synch combiner and feed the RGB to the RGB.

Jo22 wrote on 2024-11-25, 21:18:

If you build a special cable and use a DOS TSR, you can output 320x200 256c at ~15 KHz without interlacing. This has less flick […]
Show full quote

If you build a special cable and use a DOS TSR, you can output 320x200 256c at ~15 KHz without interlacing. This has less flicker than using a converter box.
The 200 line mode is interesting for those mode 13h games, which use MCGA.

Realistically speaking, though, VGA cards never did output them that way. They always used 400 lines at ~31 KHz, so it was 320x400 or 640x400 to the VGA monitor.

Also, even if you add the TSR to autoexec.bat, the TSR isn't being loaded until the PC has fully booted.
You won't see the BIOS text if you power on the PC first time, the VGA timings will confuse -if not damage- the 1084S monitor.
So in practice the 1084S can be turned on only after the TSR has been run.

maxtherabbit wrote on 2024-11-25, 22:05:

Using the VGATV TSR as mentioned is a great tool to play certain games in "native" 15kHz, but it is too finicky of a solution for me to recommend it as a primary display

1 I add the TSR to autoexec.bat and turn off the computer

2 I have a Trident TVGA 8900C VGA card. This seems to be compatible with software 15khz.

3 I connect that card via VGA cable to something like this.

4 I hook this vga->SCART cable up to this https://ultimatemister.com/product/scart-rgb-to-1084-db9/ which, again, worked great for using my snes.

5 I connect that cable to the 1084S.

6 I turn on the computer but I wait with turning on the 1084S until DOS has booted.

7 VGA magic on my RGB screen?

Also, how well would a setup like the one outlined above handle mode 03h?

boggit wrote on 2024-11-30, 10:34:

Also, how well would a setup like the one outlined above handle mode 03h?

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS).

This is like VGA 256,000 colors but at a tv refresh rate. (CGA but with more colors)

As such using a sync converter as I outlined with the Averkey Imicro will give a very convincing 320x200 x 256 colors MCGA image.

Using the 15khz TSR on a compatible VGA card also will look great on a 1084.
.

Our discussion about “dithering “ or flicker is 100% focused on the IBM 5153 TTL CGA color monitor, (commodore never had this issue)
from ibms EGA card onward it would have been trivial to support “320x200” with an 88 color (256 pattern) pallet on TTL CGA by simply outputting a 640x200 16 color dithering in pairs for the appearance of 320x200 with a wider color pallet.

Later “EGA/VGA” games would output 640x200 16 color CGA and manually dithered to improve the appearance of 256 color graphics downgraded to CGA 16 color.
This was however very slow while having the mythical DAC automattically perform the dithering to a pallet on CGA monitors would have been fast since the cpu would not need to do anything.

Clear as mud?

rmay635703 wrote on 2024-11-30, 21:05:

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS). […]
Show full quote

boggit wrote on 2024-11-30, 10:34:

Also, how well would a setup like the one outlined above handle mode 03h?

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS).

This is like VGA 256,000 colors but at a tv refresh rate. (CGA but with more colors)

As such using a sync converter as I outlined with the Averkey Imicro will give a very convincing 320x200 x 256 colors MCGA image.

Using the 15khz TSR on a compatible VGA card also will look great on a 1084.
.

Our discussion about “dithering “ or flicker is 100% focused on the IBM 5153 TTL CGA color monitor, (commodore never had this issue)
from ibms EGA card onward it would have been trivial to support “320x200” with an 88 color (256 pattern) pallet on TTL CGA by simply outputting a 640x200 16 color dithering in pairs for the appearance of 320x200 with a wider color pallet.

Later “EGA/VGA” games would output 640x200 16 color CGA and manually dithered to improve the appearance of 256 color graphics downgraded to CGA 16 color.
This was however very slow while having the mythical DAC automattically perform the dithering to a pallet on CGA monitors would have been fast since the cpu would not need to do anything.

Clear as mud?

I see! Interesting!

Would the devices/cables/converters I listed above work for going the TSR rote?

Also, in 03h on such a setup. Would the characters be 8x8 like in CGA or 8x16 like in VGA?

boggit wrote on 2024-11-30, 21:15:

I see! Interesting! […]
Show full quote

rmay635703 wrote on 2024-11-30, 21:05:

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS). […]
Show full quote

boggit wrote on 2024-11-30, 10:34:

Also, how well would a setup like the one outlined above handle mode 03h?

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS).

This is like VGA 256,000 colors but at a tv refresh rate. (CGA but with more colors)

As such using a sync converter as I outlined with the Averkey Imicro will give a very convincing 320x200 x 256 colors MCGA image.

Using the 15khz TSR on a compatible VGA card also will look great on a 1084.
.

Our discussion about “dithering “ or flicker is 100% focused on the IBM 5153 TTL CGA color monitor, (commodore never had this issue)
from ibms EGA card onward it would have been trivial to support “320x200” with an 88 color (256 pattern) pallet on TTL CGA by simply outputting a 640x200 16 color dithering in pairs for the appearance of 320x200 with a wider color pallet.

Later “EGA/VGA” games would output 640x200 16 color CGA and manually dithered to improve the appearance of 256 color graphics downgraded to CGA 16 color.
This was however very slow while having the mythical DAC automattically perform the dithering to a pallet on CGA monitors would have been fast since the cpu would not need to do anything.

Clear as mud?

I see! Interesting!

Would the devices/cables/converters I listed above work for going the TSR rote?

Also, in 03h on such a setup. Would the characters be 8x8 like in CGA or 8x16 like in VGA?

On a Commodore 1084 “CGA Analog ” Screen (not in TTL mode). Using VGA through an averkey imicro would interlace the vga characters into a psuedo 720x400 (or 350) text mode or a psuedo interlaced 640x480 graphics mode.

I’ve done just this on my newer Magnavox Amiga monitor which is very similar to a Commodore 1084. Depending on the screen mode the flicker goes from barely noticeable to dot crawl on the edges if it’s not a very compatible resolution. The screen for being 15khz is fairly clear in vga modes but flicker is definitely possible.

rmay635703 wrote on 2024-11-30, 22:40:

boggit wrote on 2024-11-30, 21:15:

I see! Interesting! […]
Show full quote

rmay635703 wrote on 2024-11-30, 21:05:

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS). […]
Show full quote

Commodore screens due to the Amiga almost universally support 15khz RGB+s analog (and CVBS).

This is like VGA 256,000 colors but at a tv refresh rate. (CGA but with more colors)

As such using a sync converter as I outlined with the Averkey Imicro will give a very convincing 320x200 x 256 colors MCGA image.

Using the 15khz TSR on a compatible VGA card also will look great on a 1084.
.

Our discussion about “dithering “ or flicker is 100% focused on the IBM 5153 TTL CGA color monitor, (commodore never had this issue)
from ibms EGA card onward it would have been trivial to support “320x200” with an 88 color (256 pattern) pallet on TTL CGA by simply outputting a 640x200 16 color dithering in pairs for the appearance of 320x200 with a wider color pallet.

Later “EGA/VGA” games would output 640x200 16 color CGA and manually dithered to improve the appearance of 256 color graphics downgraded to CGA 16 color.
This was however very slow while having the mythical DAC automattically perform the dithering to a pallet on CGA monitors would have been fast since the cpu would not need to do anything.

Clear as mud?

I see! Interesting!

Would the devices/cables/converters I listed above work for going the TSR rote?

Also, in 03h on such a setup. Would the characters be 8x8 like in CGA or 8x16 like in VGA?

On a Commodore 1084 “CGA Analog ” Screen (not in TTL mode). Using VGA through an averkey imicro would interlace the vga characters into a psuedo 720x400 (or 350) text mode or a psuedo interlaced 640x480 graphics mode.

I’ve done just this on my newer Magnavox Amiga monitor which is very similar to a Commodore 1084. Depending on the screen mode the flicker goes from barely noticeable to dot crawl on the edges if it’s not a very compatible resolution. The screen for being 15khz is fairly clear in vga modes but flicker is definitely possible.

No no, I meant the VGATV/Soft15khz method, using the specific configuration that I proposed in this post.

boggit wrote on 2024-11-29, 20:12:

Ok so what about this solution […]
Show full quote

Ok so what about this solution

BitWrangler wrote on 2024-11-25, 21:11:

What VGA cards are you using? If it's Trident, Cirrus Logic and a couple of others, you can change the output to 15khz in DOS with a TSR. Then all you have to do is make a synch combiner and feed the RGB to the RGB.

Jo22 wrote on 2024-11-25, 21:18:

If you build a special cable and use a DOS TSR, you can output 320x200 256c at ~15 KHz without interlacing. This has less flick […]
Show full quote

If you build a special cable and use a DOS TSR, you can output 320x200 256c at ~15 KHz without interlacing. This has less flicker than using a converter box.
The 200 line mode is interesting for those mode 13h games, which use MCGA.

Realistically speaking, though, VGA cards never did output them that way. They always used 400 lines at ~31 KHz, so it was 320x400 or 640x400 to the VGA monitor.

Also, even if you add the TSR to autoexec.bat, the TSR isn't being loaded until the PC has fully booted.
You won't see the BIOS text if you power on the PC first time, the VGA timings will confuse -if not damage- the 1084S monitor.
So in practice the 1084S can be turned on only after the TSR has been run.

maxtherabbit wrote on 2024-11-25, 22:05:

Using the VGATV TSR as mentioned is a great tool to play certain games in "native" 15kHz, but it is too finicky of a solution for me to recommend it as a primary display

1 I add the TSR to autoexec.bat and turn off the computer

2 I have a Trident TVGA 8900C VGA card. This seems to be compatible with software 15khz.

3 I connect that card via VGA cable to something like this.

4 I hook this vga->SCART cable up to this https://ultimatemister.com/product/scart-rgb-to-1084-db9/ which, again, worked great for using my snes.

5 I connect that cable to the 1084S.

6 I turn on the computer but I wait with turning on the 1084S until DOS has booted.

7 VGA magic on my RGB screen?

Anyone? Not too keen on ordering stuff from the interwebs that won't work with my intended use case.

As I've said, it will "work" to the extent that VGATV ever works. Certain software doesn't work properly with it, and I would NOT recommend this as a plan for a primary display unless you also have a 31kHz capable monitor close at hand to connect to the system

Jo22 wrote on 2024-11-29, 04:15:

The EGA Wonder 800 could do full EGA on an Hercules and CGA monitor, but the image was very flickery.

Off-Topic Tangent Alert:

I actually have an EGA Wonder 800 at my Dad's house that I bought on-line some years ago for another intended purpose.

The EGA Wonder 2.3 and the EGA Wonder 800 (not the plus!) support 25kHz (640x400) monitors, like the ones that came with the Olivetti M24 and AT&T 6300, and these cards can display EGA graphics on them.

On such monitors, these cards even support some crazy 752 x 410 mode that squeezes the best possible resolution out of them. ATI shipped special drivers with these cards for GEM and Windows to take advantage of these non-standard modes.

I really hope to get around to getting the Olivetti monitor to work with the EGA Wonder 800 this way some day soon, but that project has been a bit on hold since the Olivetti machine itself stopped working due to a faulty power supply.

I guess I could still try getting it to work by plugging the card into another system and running the monitor from there. But it would be really cool if I could get it running in the actual Olivetti system as the dream upgrade I was longing for as a kid.

I know this was off-topic, but it really shows how capable these ATI cards were in getting more out of older monitors than what they were initially designed to deliver. The same with monochrome monitors.

I've also been playing with an IBM 5151 Monochrome monitor attached to a VGA Wonder 16, getting it to support EGA modes with 16 shades of green, even though the monitor only supports two intensity modes. ATI implemented this through the magic of pulse-width modulation (PWM). That's why I was wondering if the same trick was also used to support 64 colors on CGA monitors. The EGA Wonder documentation does explicitly mention the following:

ATI's proprietary technique maintains a palette of 64 colors for EGA software.

Alright, nostalgia trip over, back to our regularly scheduled programming. 😅

maxtherabbit wrote on 2024-12-02, 15:24:

As I've said, it will "work" to the extent that VGATV ever works. Certain software doesn't work properly with it, and I would NOT recommend this as a plan for a primary display unless you also have a 31kHz capable monitor close at hand to connect to the system

Fair enough! I was mostly wondering if there was anything in the device/hardware configuration that I specified that was off.

I get what the drawbacks are, but it might be worth testing.

boggit wrote on 2024-12-02, 19:55:

maxtherabbit wrote on 2024-12-02, 15:24:

As I've said, it will "work" to the extent that VGATV ever works. Certain software doesn't work properly with it, and I would NOT recommend this as a plan for a primary display unless you also have a 31kHz capable monitor close at hand to connect to the system

Fair enough! I was mostly wondering if there was anything in the device/hardware configuration that I specified that was off.

I get what the drawbacks are, but it might be worth testing.

VICTORY!