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Possible to do RGB mod for 2600 or 7800?

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Someone was able to make RGB mod for Intellivision. Can something like it be done for Atari system? The original video chip could only output composite on Intellivision which are then fed into RF modulator. TIA for 2600 outputs S-Video like signal in the form of sync, chroma and 3 luma signals which went through resistor ladder and combined to make composite.

 

I believe there are enough detail on TIA chip that it may be possible to engineer an alternate design that outputs RGB instead. Or is 2600 a complicated beast to make RGB capable TIA clone?

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This is just my opinion, but if you can get S-Video from those systems, and you're using a CRT, I would just do that. RGB modding seems to require 2X or 3X the price, and on a CRT the difference will be negligible.

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Yes. This is possible. My 2600 supports VGA output. And yes, you *CAN* see the improvement over S-Video.

Even on a 14" Amiga monitor the difference is quite noticable. On a 10ft projection screen it is a massive improvement.

No problems at all with VGA....perfect pixels with no color artifacting at all. You can't achieve this with NTSC.

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VGA often gets interchanged for RGB, for instance the amiga monitors were 15khz per line RGB monitors, VGA is 32khz per line RGB monitors (minimum), the main thing being, unless you have a special monitor (ie really old multisync's like the radiation box I have) VGA screens are not going to accept a 15khz signal

 

that being said Im not a amiga expert and they might have made monitors that supported both, but I doubt it would work plugged into a modern monitor (it may work plugged into the VGA port of a TV, TV's support both and are usually decent about hooking old analog RGB machines up that way)

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VGA often gets interchanged for RGB, for instance the amiga monitors were 15khz per line RGB monitors, VGA is 32khz per line RGB monitors (minimum), the main thing being, unless you have a special monitor (ie really old multisync's like the radiation box I have) VGA screens are not going to accept a 15khz signal

 

that being said Im not a amiga expert and they might have made monitors that supported both, but I doubt it would work plugged into a modern monitor (it may work plugged into the VGA port of a TV, TV's support both and are usually decent about hooking old analog RGB machines up that way)

 

No, this was VGA compatible. I have screenshots taken from a Viewsonic P815 21" CRT, a 29GA 29" CRT, and a Dell 1702 LCD. It was also tested with a few Epson and Viewsonic projectors. And a Sony I think. These are all "modern" computer monitors, syncing at 31.4 kHz or what ever VGA actually is. I can't upload right now, but the pics are around.

Edited by cwilkson

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No, this was VGA compatible. I have screenshots taken from a Viewsonic P815 21" CRT, a 29GA 29" CRT, and a Dell 1702 LCD. It was also tested with a few Epson and Viewsonic projectors. And a Sony I think. These are all "modern" computer monitors, syncing at 31.4 kHz or what ever VGA actually is. I can't upload right now, but the pics are around.

What mod did you use?

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What mod did you use?

 

I used the CyberTech VGA, of course. :) Even after all these years it's still the only one that can do VGA or component video on a 2600, AFAIK.

 

Here are some screenshots.

 

Pitfall II is from a ViewSonic P815 monitor (21") which was my main PC monitor at the time. The video quality is most noticeable in the lack of color bleed around the tree trunks and the red cross.

Especially around the trees. It's impossible to do that in NTSC, even with the new CyberTech S-video card.

 

River Raid is from a Commodore 1942 monitor (13"). Someone had asked for a "scan lines" option and wanted to know what it looked like on an Amiga monitor. The option is selectable with a switch on the CyberTech VGA card but could be done using the BW/color switch at power on. These pics show the difference.

post-260-0-33225700-1434122290_thumb.jpg

post-260-0-64447500-1434122358_thumb.jpg

post-260-0-33957800-1434122360_thumb.jpg

Edited by cwilkson

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I used the CyberTech VGA, of course. :) Even after all these years it's still the only one that can do VGA or component video on a 2600, AFAIK.

Where can I find more information / where to buy this mod? I'm quite new on the 2600 scene and I was under the impression that Svideo was the best it could to with mods. Does your CyberTech VGA have a RGBS/Scart option? (15kHz with csync, unlike 31kHz VGA with distinct hsync and vsync)

Edited by jarreboum

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Years ago, a guy was developing a "2600 on a chip" and he had RGB out on it! It seemed to disappear right before the first Flashback unit came out.

 

Also, doesn't the France version of the 7800 have RGB out?

Edited by SoundGammon

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Where can I find more information / where to buy this mod? I'm quite new on the 2600 scene and I was under the impression that Svideo was the best it could to with mods. Does your CyberTech VGA have a RGBS/Scart option? (15kHz with csync, unlike 31kHz VGA with distinct hsync and vsync)

 

 

Years ago, a guy was developing a "2600 on a chip" and he had RGB out on it! It seemed to disappear right before the first Flashback unit came out.

 

Also, doesn't the France version of the 7800 have RGB out?

 

 

Where can I find more information / where to buy this mod? I'm quite new on the 2600 scene and I was under the impression that Svideo was the best it could to with mods. Does your CyberTech VGA have a RGBS/Scart option? (15kHz with csync, unlike 31kHz VGA with distinct hsync and vsync)

 

It was never produced due to lack of interest. I couldn't believe it. It was ready for beta testing, but no takers. So it sits on a shelf, unused (except by me). As it sits, the only CyberTech mods are VGA, Component, S-video, and Composite. S-video and Composite work with NTSC and PAL (and probably SECAM). Those SCART options could probably be done with the existing hardware, but there would have to be a lot of interest (a lot) for me to pull it out of mothballs.

 

Years ago, a guy was developing a "2600 on a chip" and he had RGB out on it! It seemed to disappear right before the first Flashback unit came out.

 

Also, doesn't the France version of the 7800 have RGB out?

 

There have been many FPGA versions, of varying quality, over the years. You might be thinking of Cassidy who went on to do the Flashback. (I think that was Cassidy?) If you're doing that, it's trivial because you have open access to all of the internal signals. Plus you can create your own signals specific to the task and whatever format you want.

 

Mine uses the stock TIA outputs and umm....upconverts(?) them to VGA. I don't really have a good word for it. I take what's coming from the TIA, clean it up a lot, standardize the colors, then output it to the world.

It's actually got a *negative* conversion loss. It's not trivial at all. In fact, we all thought it was theoretically impossible, even with loss, until I got too much Mt. Dew in me one day and just DID it. :P But I had thought about how to do it for years before actually trying.

 

I have one of those RGB 7800s. It's pretty nice. But IIRC it only syncs to 15.7kHz. Which rules out using most monitors. And it uses the MARIA/TIA outputs as-is, without compensating for unit to unit variation in the chroma delay.

Also, you can't make them anymore. The parts don't exist. :(

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Is it real RGB for the French 7800 though? The French NES had a fake RGB out in the form of a Composite signal converted to RGB: the PPU only output chroma and luma. Nintendo couldn't be arsed to make a new RGB chip just for the French and instead added a board to convert Composite. Needless to say the "RGB" picture of the French NES is quite ugly, possibly uglier than original Composite.

 

I'm surprised you couldn't find support for RGB out, having RGB is all the rage in retrogaming nowadays. People hunt for PVMs and BVMs, threads with hundreds of pages are made on forums dedicated to get the best of your old consoles, how to mod them to get RGB (a very complex and expensive NES mod has been out since last year and is selling very well), and how to pass RGB to modern TVs through expensive upscalers. The Japan-made Framemeister costs around $300 and is the goto upscaler for retro-enthusiasts, even though they have to import it from Japan. Europeans enthusiasts hunt Trinitrons as supposedly the prettiest looking non-professional monitor, as all European tubes had RGB Scart inputs.

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Is it real RGB for the French 7800 though? The French NES had a fake RGB out in the form of a Composite signal converted to RGB: the PPU only output chroma and luma. Nintendo couldn't be arsed to make a new RGB chip just for the French and instead added a board to convert Composite. Needless to say the "RGB" picture of the French NES is quite ugly, possibly uglier than original Composite.

The French 7800 does the exact same thing, in fact it even uses the same Sony video decoder chip.

 

Also the NES PPU only outputs composite video, it doesn't output separate chroma and luma signals.

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It was never produced due to lack of interest. I couldn't believe it. It was ready for beta testing, but no takers. So it sits on a shelf, unused (except by me). As it sits, the only CyberTech mods are VGA, Component, S-video, and Composite. S-video and Composite work with NTSC and PAL (and probably SECAM). Those SCART options could probably be done with the existing hardware, but there would have to be a lot of interest (a lot) for me to pull it out of mothballs.

 

The screen shots were amazing. I can't believe there wasn't more interest. I know it is a long shot, but if you ever release your VGA mod I would love to purchase one.

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The screen shots were amazing. I can't believe there wasn't more interest. I know it is a long shot, but if you ever release your VGA mod I would love to purchase one.

 

Thanks. It was really nice. I literally couldn't see the difference between CyberTech VGA and Stella output on the same monitor.

Yes, literally is the right word; the only way to tell which source was active on the monitor was to wiggle the joystick or hit the keyboard.

 

And it was mind boggling that I couldn't find testers. Crazy crazy.

 

If I ever get back to it I will announce it here for sure. Right now I'm bogged down in a new vector arcade PCB project.

Edited by cwilkson

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How did you achieve it? It's not quite my field of expertise but I'm interested in your method. Comparatively this is how Tim managed it for the NES: http://shmups.system11.org/viewtopic.php?f=6&t=47617. If I understand correctly, he's using an FPGA to monitor the RAM for colour data and to emulate the colour output part of the PPU.

 

You were talking about "upconverting" the TIA output, I would assume you would monitor the analogue colour output and approximate it to its nearest digital value from the original palette? Considering the 2600 palette is fixed and has a low number of different colours, this would effectively clean up the signal without adding much artefacts.

Edited by jarreboum

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