TheAtariKing Posted October 16, 2014 Share Posted October 16, 2014 I bought one of these GBS8200 boards on eBay. It works great with both the Amiga and Atari ST computers. Set the board to output 1024 x 768 resolution. The board must be fan cooled and the power to it should be 5 volts and at least 2 amps of current. The best LCD or Flat Panel monitors to use are 15 inch or smaller, because their native or recommended screen resolution is 1024 x 768 or less. I use an NEC AccuSync LCD 52VM monitor. Quote Link to comment Share on other sites More sharing options...
galax Posted October 16, 2014 Share Posted October 16, 2014 Does your ST have a modulator? I got my GBS-8220 to work well with the BBC Micro (which has RGB and composite sync), but it didn't seem to like the ST's separate vertical and horizontal sync). Non-modulator STs also have a composite sync, which I've heard works with the GBS, but modulator fitted STs have composite video in its place. I've been meaning to try splitting a composite sync signal out from the composite video. I've heard very mixed reports about people's successes and failures with these boards. It may be that there are production inconsistencies, different firmwares, or people are doing something different- there are long discussions about getting these to work, and some of them end with people throwing them away. Even when they can get them to work, some people can't live with the artifacts when parts of the screen change. Quote Link to comment Share on other sites More sharing options...
TheAtariKing Posted October 16, 2014 Author Share Posted October 16, 2014 PS: The Atari ST computer's monochrome mode will also greatly benefit from this board, because it upscales the 640 x 400 screen to 1024 x 768. Also, the larger the flat panel monitor, the crappier the picture. This is because LCDs and Flat Panel monitors that are larger than 15 inches also have a higher native or recommended screen resolution. Quote Link to comment Share on other sites More sharing options...
TheAtariKing Posted October 16, 2014 Author Share Posted October 16, 2014 The "artifacts" are usually caused by supplying 5 volts with less than 2 amps of current, or from using an LCD / Flat Panel monitor that has a native / recommended screen resolution that is higher than 1024 by 768. Also, the monitor MUST have an aspect ratio of 4:3. Do not use wide-screen monitors with Amiga or Atari ST computers. Quote Link to comment Share on other sites More sharing options...
TheAtariKing Posted October 16, 2014 Author Share Posted October 16, 2014 Here is a picture of the GBS8200 board in my Amiga 500 Tower. Notice how I have an 80 mm fan blowing air over the board. I am very happy with this RGB to VGA board. It is also a Flicker Fixer. Quote Link to comment Share on other sites More sharing options...
galax Posted October 16, 2014 Share Posted October 16, 2014 (edited) PS: The Atari ST computer's monochrome mode will also greatly benefit from this board, because it upscales the 640 x 400 screen to 1024 x 768. Also, the larger the flat panel monitor, the crappier the picture. This is because LCDs and Flat Panel monitors that are larger than 15 inches also have a higher native or recommended screen resolution. Does the Amiga that you are using this with have composite sync signal? The ST's monochrome mode looks much better on a 1280 by 1024 monitor, which can pixel double horizontally, checkered areas such as the desktop give quite nasty interference patterns at 1024 pixels wide. Lots of Multisync type LCD monitors support the ST's mono mode natively, I doubt the GBS would look as good as the native video straight into these monitors does. The "artifacts" are usually caused by supplying 5 volts with less than 2 amps of current, or from using an LCD / Flat Panel monitor that has a native / recommended screen resolution that is higher than 1024 by 768. Also, the monitor MUST have an aspect ratio of 4:3. Do not use wide-screen monitors with Amiga or Atari ST computers. I'm not sure that's always the case, my first tests with this board were with a 3 Amp bench power supply, and I very definitely saw artifacts then. Another problem was random 'sparkly' pixels which are scattered about occasionally. Interestingly when I used it to upscale from an SVGA signal I didn't see artifacts, so it may depend on the source resolution, among other things. It wouldn't surprise me if some people don't have artifacts, as I said before people's experiences vary widely with this board. I use it quite a bit with my BBC Micro though, the mostly black backgrounds seem to reduce the visibility of the artifacts a bit. The GBS is great for the price if you can get it to work and can't find an LCD monitor that can accept 15kHz horizontal, but it's not a patch on a decent upscaler such as an XRGB-3. Edited October 16, 2014 by galax Quote Link to comment Share on other sites More sharing options...
TheAtariKing Posted October 16, 2014 Author Share Posted October 16, 2014 (edited) The video signals used by both the Amiga and the Atari ST computers are Red, Green, Blue, H-Sync, V-Sync, and Ground. You usually can get Composite Sync by joining H-Sync and V-Sync together, but, separate H-Sync and V-Sync produces a much better quality signal. Also, higher quality RGB cables have Red-Ground, Green-Ground, and Blue-Ground, not just one ground for everything. This could account for the "artifacts". Edited October 16, 2014 by TheAtariKing Quote Link to comment Share on other sites More sharing options...
galax Posted October 16, 2014 Share Posted October 16, 2014 (edited) The video signals used by both the Amiga and the Atari ST computers are Red, Green, Blue, H-Sync, V-Sync, and Ground. You usually can get Composite Sync by joining H-Sync and V-Sync together, but, separate H-Sync and V-Sync produces a much better quality signal. Also, higher quality RGB cables have Red-Ground, Green-Ground, and Blue-Ground, not just one ground for everything. This could account for the "artifacts". No, the artifacts I am talking about are digital, they are created in the scaler; they appear when the image changes, and then disappear when the image is stable again. They look just like compression artifacts in badly encoded movies, but they disappear on a stable image. It really looks like some codec is being used to compress the video internally within the device, and the image is cleaned up at the next keyframe . I generally use recycled VGA or DVI cables and get excellent signal quality, of course all the grounds are just joined together at the ST end. Joining together the H-Sync and V-Sync outputs is generally thought to be a bad idea, you should use some logic to join these signals together. None of what I am saying is new ground, there are long threads on Atari-forum about the pros and cons of using the GBS with the ST, and how to work around some of the problems. Edited October 16, 2014 by galax Quote Link to comment Share on other sites More sharing options...
galax Posted October 16, 2014 Share Posted October 16, 2014 Here someone describes exactly the artifacts that I am talking about as a "bubble of weirdness", the inability to output 50Hz is another downside of the GBS: Still picture deinterlace: ExcellentMoving picture deinterlace: Poor. There is a "bubble" of weirdness around moving objects. e.g. moving the cursor on an archimedes desktop over icons results in the icon pixels around the cursor moving up and down.Motion artefacts: Poor - this converter changes the 50Hz BBC output to 60Hz so smooth scrolling and general motion is judderyOther comments: Random white spots appear on the screen. This seems to be unfixable as changing a screen setting or changing the voltage of the supply will eliminate them for a while but they usually return. http://www.stardot.org.uk/forums/viewtopic.php?f=3&t=8030 Quote Link to comment Share on other sites More sharing options...
TheAtariKing Posted October 16, 2014 Author Share Posted October 16, 2014 Well, I do not know about PAL, but, on NTSC systems the board works great. The ones I use are just like the one pictured. I have an Atari 1040STf and an Atari 1040STe. The RGB to VGA board works great on both computers. Quote Link to comment Share on other sites More sharing options...
TheNameOfTheGame Posted October 16, 2014 Share Posted October 16, 2014 Tried a couple of these in the past. Lots of threads here about them. I always had artifacts under /around the mouse. Tried a v3 and a v5. Never touched them again. NTSC. 1 Quote Link to comment Share on other sites More sharing options...
galax Posted October 17, 2014 Share Posted October 17, 2014 NTSC systems default to 60Hz in low/medium res, but some games & demos will force them into 50Hz. Many compact menu screens have key to toggle Hz, and there are utilities that do this too. Anything that runs only in 50Hz will look choppy through that converter, as it always converts to 60 Hz. @TheNameOfTheGame I still haven't worked out why people have such a range of experiences with these boards- some love them, some bin them in anger, I'm somewhere in the middle- they are OK for the price. Quote Link to comment Share on other sites More sharing options...
amiman99 Posted October 17, 2014 Share Posted October 17, 2014 We know it works, here is the thread: http://atariage.com/forums/topic/196606-st-scandoubler-vga-box/ Quote Link to comment Share on other sites More sharing options...
+poobah Posted October 17, 2014 Share Posted October 17, 2014 I tried several different versions of these, they all suffer from various distortions. If you really want to use one, you need to to fix up the ST hsync and vsync signals before feeding them to the board. I had better results with an AD724 s-video encoder. Quote Link to comment Share on other sites More sharing options...
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