ATI VGA Wonder on a CGA/MDA Monitor Question

[chjmartin2]

Hi,

I am curious about this and can't seem to find an internet or forum reference that has tested it out. I want to do it myself but don't have an appropriate XT in a condition to do so - yet. Specifically I am curious what capabilities you get when you hook up a TTL CGA monitor to the card or a Monochrome TTL. I can only find the ATI Wonder XL manual but it says some really interesting things. Full manual Link. Here is the monitor selection table:


If you look it says that if you use a TTL monitor that you get "shades" for EGA/CGA modes. It also shows EGA as 16/64 and CGA as 4/16. I have seen for sure 16 shades on a monochrome TTL and we know that a CGA monitor has 16 colors. I am well aware we get 320x200x16 EGA on a CGA Monitor and 320x200x16 grays EGA on a Monochrome TTL Monitor. I am curious how the 16 shades are created on the Monochrome TTL. This video shows EGA 16 on an IBM 5151 - it LOOKS like 16 shades of grey but I can't completely tell.

So now here is where it gets interesting to me. It says it can use interlace to display EGA resolutions on a TTL monitor - is that right?



So then I found a tidbit in an EGA Wonder manual (I know they are different) that gave me pause as well.


So I guess my overall question is does the VGA Wonder work the same as the EGA Wonder for EGA modes when attached to a TTL Monitor. I do not have an EGA Wonder but do have a VGA Wonder. Lastly, WHAT EXACTLY IS THE PROPRIETARY TECHNIQUE!?!? Like, does the EGA Wonder REALLY allow 64 colors on a Digital TTL Monitor that can only display 16 colors? Is it using Pulse Width Modulation or some other voodoo magic? It is truly 64 shades of gray? Can it REALLY even do 640x350x16 and not just the regular RGBI colors?

Does anybody have an EGA Wonder that can show us this ATI Magic??? Lastly, does the VGA Wonder do the same magic for EGA modes? I love CGA and I love CGA Monitors but I can't get over the fact that there might me MORE than 640x200x16 which of course using a Tandy we have seen.

Thanks,

Chris

 

[mikey99]

Many years ago, I ran my 386 clone with a VGA Wonder attached to a PCjr color monitor !!!
My NEC 3D monitor was being repaired and I still wanted to use the computer.
As I recall it looked pretty bad, but I think it was simulating EGA colors.

At the time I thought this was a cool function, but I was happy when I got the NEC monitor
fixed

I still have the ATI manual, here's an excerpt from that page:

 

[Eudimorphodon]

So I guess my overall question is does the VGA Wonder work the same as the EGA Wonder for EGA modes when attached to a TTL Monitor. I do not have an EGA Wonder but do have a VGA Wonder.

ATI used a proprietary ASIC filled with magic smoke to do these wonderful tricks, and my vague understanding is that they used (almost) exactly the same version on the EGA/VGA Wonders, which is why the VGA Wonder only supports up to EGA modes instead of being updated to do even more black magic to fake VGA modes. (A reasonable explanation why they didn't is the 480 lines of VGA would simply be too tall and would go well into the overscan of a normally adjusted CGA monitor.)

Lastly, WHAT EXACTLY IS THE PROPRIETARY TECHNIQUE!?!? Like, does the EGA Wonder REALLY allow 64 colors on a Digital TTL Monitor that can only display 16 colors? Is it using Pulse Width Modulation or some other voodoo magic?

So, yes, that's the short answer; it uses interframe flicker between pairs of the available RGBI colors to fake the full EGA palette (or, even worse, bangs on various combinations of the video and intensity lines if the connected monitor is an MDA monochrome to do more than 4 grays), so the end result is neither particularly authentic nor ergonomic. (The monochrome rendition might actually qualify as torture under the Geneva Convention if displayed on anything but a very long persistence green monitor, and likewise the 30hz interlaced necessary to display high-res EGA and Hercules on CGA monitors is just... ugh. I have no idea how Amiga users ever put up with it.) Like a dancing bear it's more remarkable for the fact that it does it at all than does it well.

Of course, saying this isn't meant to try to talk anyone out of these cards, they are in fact awesome simply for their novelty value, and they can really be useful in some niche applications, like upgrading portables with fixed frequency monitors to better than CGA graphics.

 

[chjmartin2]

ATI used a proprietary ASIC filled with magic smoke to do these wonderful tricks, and my vague understanding is that they used (almost) exactly the same version on the EGA/VGA Wonders, which is why the VGA Wonder only supports up to EGA modes instead of being updated to do even more black magic to fake VGA modes. (A reasonable explanation why they didn't is the 480 lines of VGA would simply be too tall and would go well into the overscan of a normally adjusted CGA monitor.)

So, yes, that's the short answer; it uses interframe flicker between pairs of the available RGBI colors to fake the full EGA palette (or, even worse, bangs on various combinations of the video and intensity lines if the connected monitor is an MDA monochrome to do more than 4 grays), so the end result is neither particularly authentic nor ergonomic. (The monochrome rendition might actually qualify as torture under the Geneva Convention if displayed on anything but a very long persistence green monitor, and likewise the 30hz interlaced necessary to display high-res EGA and Hercules on CGA monitors is just... ugh. I have no idea how Amiga users ever put up with it.) Like a dancing bear it's more remarkable for the fact that it does it at all than does it well.

Of course, saying this isn't meant to try to talk anyone out of these cards, they are in fact awesome simply for their novelty value, and they can really be useful in some niche applications, like upgrading portables with fixed frequency monitors to better than CGA graphics.

I still need to see this in action. The VGA Wonder manual doesn't specifically state it does this but the EGA Wonder does. I just really like my CGA Monitor and want to stay authentic to the XT that I have and feel like this is a good method to get 16 color Sierra games and such but really just HAVE to see the effect of an interlaced 640x350x16 color image on said CGA Monitor. Did EGA do 320x200x16 out of 640? Good to know it is a 30 Hz image though. I always felt like if you could way over-modulate the CGA TTL that you could change the pixel on the fly rather than waiting for the next refresh just don't know if the monitor could keep up.

 

[Eudimorphodon]

always felt like if you could way over-modulate the CGA TTL that you could change the pixel on the fly rather than waiting for the next refresh just don't know if the monitor could keep up.

In theory it'd certainly be possible to just double the effective pixel clock (giving you effectively a 1280x400x16 interlaced pretending to be 640x350x64) and do subpixel pattern-dithering, but I don't *think* that's what the ATI cards do. (There was a thread about them a couple years ago where this was discussed, and my recollection was that it was pretty authoritatively stated that it was interframe dithering instead.) It's possible there might be switching speed limitations in vintage TTL monitors that would make cranking up the pixel clock that high problematic.

So far as I know the EGA and VGA Wonders use the same dithering (in fact the last versions of the EGA Wonder were actually VGA Wonders missing the analog port), but it would certainly be interesting if someone who has the card would make a YouTube video about them and show them in action comparing their output on CGA monitor to the real thing. One thing that might not come through, though, is the flicker. I never owned an EGA/VGA wonder myself, but I did play with one of their earlier Graphics Solution cards that did similar tricks to let CGA and MDA monitors run each other's software interchangeably; the card was connected to a Princeton Graphics MAX-12 Amber monitor that could natively handle both MDA/Hercules and CGA in 16 shades of grey, and here's what I remember. (With the proviso that this memory is over 30 years old

1: The "additional" shades of gray you got when emulating CGA (or Plantronics) on an MDA monitor looked great from a distance but flickered enough to give you a headache if you actually sat in front of it for any length of time, and,

2: If you did the reverse, ran Hercules in interlaced mode with the monitor pretending to be CGA then the interlace flicker was about equally bad. Maybe slightly more usable than on an actual color monitor because of the amber phosphor's longer persistence.

 

[chjmartin2]

So far as I know the EGA and VGA Wonders use the same dithering (in fact the last versions of the EGA Wonder were actually VGA Wonders missing the analog port), but it would certainly be interesting if someone who has the card would make a YouTube video about them and show them in action comparing their output on CGA monitor to the real thing. One thing that might not come through, though, is the flicker.

I have an 8088 XT, a brand new XT-CF ECO-LITE, a VGA Wonder 16 (known to work in an 8 bit slot) and plan on testing this out. I have a Monochrome TTL monitor and a CGA RGB Monitor and of course VGA. I am anxious to get it all working although I am sure it won't just be plug and play. Anyway, if it does the fancy EGA trick then I will be happy to share, but if not, I will be on the search for an EGA Wonder. Any particular programs I should try beyond just using Compushow?

 

[Trixter]

For 320x200x16 and 640x200x16 EGA modes on a CGA monitor, this works perfectly. For the 350-line 64-color modes... well, let's just say that the marvel is not that the bear dances well, but that the bear dances at all.

 

[chjmartin2]

Like a dancing bear it's more remarkable for the fact that it does it at all than does it well.

well, let's just say that the marvel is not that the bear dances well, but that the bear dances at all.

It's funny that you both used the same analogy. If you have a setup that can demonstrate this then I'd be happy to see it. I have a ways to go to test the set up on my own and my capture rig isn't particularly useful compared to where I have the space to work on my XT. Regardless it is on my list to see this particular dancing bear.

 

[chjmartin2]

Ok so after fighting with an XT-IDE, Gotek floppy emulator and a Monotech Deluxe Floppy card on my Vendex 888-XT and then gave up trying to get it to work. I am sure it was some kind of conflict with on-board devices. I pivoted and went to my Vendex Headstart II and that got a long much better the the Gotek/Monotech Deluxe Floppy. (Oddly I couldn't get the Gotek to work with the on-board floppy controller which is compatible with a 1.44 meg drive.) I also was able to get the XT-IDE to recognize CF drives but didn't have a bootable one. I couldn't get the Monotech Deluxe Floppy and the XT-IDE to play nice together but didn't try that hard. Anyway, I used the Gotek and a USB drive and then got the ATI VGA Wonder 16 running. I have tried to upload my resulting images here but keep running into image size limits. It is not wildly impressive as indicated and it certainly has flicker but I'm not sure that they are getting to the color pallet simply by a 30 Hz blend. I am going to take some slow motion video with my phone to see if I can figure it out. I am also not convinced that it is really displaying 350 lines as some text doesn't appear correct. I need to get the CF adapter working and if anybody knows if the Monotech Deluxe Floppy and an XT IDE lite can play nice together would appreciate insight.