GBS 8200/8220 CFW Project

[NoAffinity]

So, I wanted to revisit chaining the GBS w/ rama firmware to OSSC, for a specific use case.

Playing Neo Geo MVS on a Retrotek supegun (yes its cheap, but it works...pretty well)->SCART->OSSC, I optimized the OSSC, got it looking great, but would get infrequent momentary audio drop-outs. The MVS is known to need a bit of extra tuning w/ OSSC via 'H-PLL Post Coast' and 'HSync tolerance' tweaks. I'm attributing it to either a related tolerance mis-match, or something else unknown that isn't quite aligned with the MVS' output.

So, I tested the chain of:
MVS 1-slot -> Retrotek Supergun SCART output -> GBS-8200 w/ rama firmware, VGA output -> VGA-to-YPbPr transcoder -> OSSC YPbPr input

The GBS is set to 1280x1024 output, so OSSC is treating it as pass-thru.

I tested:
1) OSSC @ default settings, with minor tweaks to H. Backporch and V. Backporch to center the image
2) OSSC w/ attempted optimization

In the capture, the image ratio appears to be about comparable between both settings. On my flat panel, the optimized image is more compressed, much closer to what I assume is native 1280x1024.

Either way, it looks pretty darn good, and most importantly, no audio drop out.

And there was some recent questions about chaining GBS w/ rama firmware -> OSSC, so hear you go:
https://youtu.be/XAmvp0XqhoE

And here's a direct download link of the original video file: https://we.tl/t-4H5blxp2HD

The option you present is very interesting, but tell me what would be gained by chaining these 2 devices? I would think that the correct order would be OSSC and then GBS Control, especially for cases like SNES where framerate is a problem for many TVs and I think that with GBS Control this could be improved. And I have not wanted to buy an OSSC given its compatibility problems in resolution and framerate with many TVs on the market. And changed a little the subject you can pass us photos and model of your transcoder from VGA to YPbPr, I am looking for one for Dreamcast since VGA is quite problematic in my Setup it is the only console with this output and it is a problem for me.

The sync problem exists at the OSSC. Putting the OSSC first in the chain defeats the purpose. The GBS handles the sync better, and "smooths" the signal before going to a the OSSC, which is ultimately only the chain as an expensive Component-to-HDMI converter. But I already own it, and I'm not going to spend more money on a purpose-built converter.

I tested GBS @ pass thru this morning, sending 240p to the OSSC. Using my stock "MVS direct" optimizations, with a few minor tweaks, I got it looking every bit as good as if the GBS isn't in the chain, but again, with the benefit of eliminating the drop-outs.

The VGA-to-YPbPr transcoder I have is the Retrotek model: https://www.retrotekshop.com/products?pn=VGACTV2

[Shiver_169]

The sync problem exists at the OSSC. Putting the OSSC first in the chain defeats the purpose. The GBS handles the sync better, and "smooths" the signal before going to a the OSSC, which is ultimately only the chain as an expensive Component-to-HDMI converter. But I already own it, and I'm not going to spend more money on a purpose-built converter.

I tested GBS @ pass thru this morning, sending 240p to the OSSC. Using my stock "MVS direct" optimizations, with a few minor tweaks, I got it looking every bit as good as if the GBS isn't in the chain, but again, with the benefit of eliminating the drop-outs.

The VGA-to-YPbPr transcoder I have is the Retrotek model: https://www.retrotekshop.com/products?pn=VGACTV2

I appreciate your follow-up. I think GBS would be better after OSSC since sync failure is not a problem of the device itself, but rather a problem with consoles that were designed for CRT technologies from the 80s ando 90s that was not so sensitive to framerates as is the HDMI standard in use right now. And normally people use the OSSC chained to another device to normalize the sync and in this way leave the work of escalation to the OSSC, which I understand and Rama has openly said is better in terms of image quality.

[EmKIronFist]

I tested GBS @ pass thru this morning, sending 240p to the OSSC. Using my stock "MVS direct" optimizations, with a few minor tweaks, I got it looking every bit as good as if the GBS isn't in the chain, but again, with the benefit of eliminating the drop-outs.

You have the Clock generator installed, right? Do you get any dropouts with 240p/480i switching? I started getting extremely brief dropouts for 240p/480i transitions. The power for my clockgen board is wired up to C47, which the wiki says is fine but I've noticed almost everyone is using C48.

[rama]

You have the Clock generator installed, right? Do you get any dropouts with 240p/480i switching? I started getting extremely brief dropouts for 240p/480i transitions. The power for my clockgen board is wired up to C47, which the wiki says is fine but I've noticed almost everyone is using C48.

This could be the clockgen frequency adjustments that occur on transitions.
The intent is to slowly adjust to the new clock, so that the sink device don't notice a change.
If the sink sees a change anyway, that could then lead to a sync loss.

So I wouldn't suspect the clockgen installation, but rather the algorithm.
It may either measure the new frequency wrong, or it may transition to the new frequency in a bad way.
I'll have to tune this a bit more, but I'm confident I can improve this.

[EmKIronFist]

This could be the clockgen frequency adjustments that occur on transitions.
The intent is to slowly adjust to the new clock, so that the sink device don't notice a change.
If the sink sees a change anyway, that could then lead to a sync loss.

So I wouldn't suspect the clockgen installation, but rather the algorithm.
It may either measure the new frequency wrong, or it may transition to the new frequency in a bad way.
I'll have to tune this a bit more, but I'm confident I can improve this.

Thank you for explaining!

This explains a lot, because I noticed that when feeding the GBS a signal from the Retrotink 2X Classic in linedouble mode (480p), the dropouts stop, even though I would normally get dropouts if I connected my Retrotink directly to my display.

[NoAffinity]

The sync problem exists at the OSSC. Putting the OSSC first in the chain defeats the purpose. The GBS handles the sync better, and "smooths" the signal before going to a the OSSC, which is ultimately only the chain as an expensive Component-to-HDMI converter. But I already own it, and I'm not going to spend more money on a purpose-built converter.

I tested GBS @ pass thru this morning, sending 240p to the OSSC. Using my stock "MVS direct" optimizations, with a few minor tweaks, I got it looking every bit as good as if the GBS isn't in the chain, but again, with the benefit of eliminating the drop-outs.

The VGA-to-YPbPr transcoder I have is the Retrotek model: https://www.retrotekshop.com/products?pn=VGACTV2

I appreciate your follow-up. I think GBS would be better after OSSC since sync failure is not a problem of the device itself, but rather a problem with consoles that were designed for CRT technologies from the 80s ando 90s that was not so sensitive to framerates as is the HDMI standard in use right now. And normally people use the OSSC chained to another device to normalize the sync and in this way leave the work of escalation to the OSSC, which I understand and Rama has openly said is better in terms of image quality.

The hiccup with the MVS is at the OSSC. Every time it drops out, the red LED on the OSSC flashes momentarily and the frequency info on the screen blips momentarily, confirming the OSSC is losing signal. I also tested, and am currently running, a Tim Worthington AV-Driver board between MVS+Retrotek supergun and OSSC, and it's working great, no drop-outs. The AV-Driver is doing it's job correcting the signal so that it is suitable for OSSC, as does the GBS.

If I go MVS direct to OSSC and then chain another device, the blip at the OSSC will propagate to the rest of the chain. The drop-outs also don't occur with other game boards swapped into the identical setup.

@EmKIronFist yes I have the clockgen installed.

:edit: sorry, i need to crrect the statement about the AV-Driver configuration. It is MVS->AV-Driver->OSSC. The retrotek supergun is after the AV-Driver being split off of a jamma pass-thru adapter. There is no video coming off the supergun in that scenario. So, MVS->AV-Driver->OSSC works fine, no drop-outs. MVS->supergun->GBS->OSSC works fine, no drop-outs. MVS->Supergun->OSSC or MVS->OSSC produces drop-outs.

[mutmut02]

Hi. I've started building my own GBS-C, mainly for the downscaling possibilites. Now I have 3 questions that may sound a bit dumb, but I'll ask them anyways :

1/ Instead of a jumper, could I bridge the 2 points underneath, in the same fashion as the RGB pots bypass ? I was thinking about using a resitance leg in order to do that.

I'd like to make my own output cable DB15 -> Male scart. My question is

2/ Which pins on the VGA output should I use as the sync pin on the scart connector ?

I also would like to try the upsacling part and make my own Female Scart -> DB15 cable.

3/ I understand that a Sync stripper is no longer required. Can you confirm this ? How should I connect the sync pin on the VGA side ?

Thanks

[DanAdamKOF]

Has anyone used GBS-Control with an x68000? It outputs a 55hz signal, either 480p or 240p (or rarely 384p), so this might be throwing it off.

I first tried it with separate H+V sync, using 480p@55hz, and I got a rolling garbage signal at best. Then I combined H+V into one signal (didn't use a proper sync combiner circuit, just doing a quick test) and got a non-rolling garbage signal. Tried this with and without the 100ohm resistor linking Sync to Ground and got the same result. I don't think it's the crude sync combining as I've heard this works fine for x68000 (then again it's a 15 year old forum post saying so ).

This is without using bypass mode, as my intent is to scale the 480p signal for better looking captures.

[NoAffinity]

@mutmut02 I can answer the easy question. Yes you can short the pins in any fashion you like as long as it creates continuity.

Sent from my SM-G955U using Tapatalk

[Shiver_169]

Hi. I've started building my own GBS-C, mainly for the downscaling possibilites. Now I have 3 questions that may sound a bit dumb, but I'll ask them anyways :

1/ Instead of a jumper, could I bridge the 2 points underneath, in the same fashion as the RGB pots bypass ? I was thinking about using a resitance leg in order to do that.

I'd like to make my own output cable DB15 -> Male scart. My question is

2/ Which pins on the VGA output should I use as the sync pin on the scart connector ?

I also would like to try the upsacling part and make my own Female Scart -> DB15 cable.

3/ I understand that a Sync stripper is no longer required. Can you confirm this ? How should I connect the sync pin on the VGA side ?

Thanks

Hi, I give you some answers based on my experience, I hope someone else can complement them.

1) I do not quite understand what you mean at this point since joining the dots with excess wire of a resistance is just what is recommended, see the RetroRGB video for more reference in this regard.
2) The GBS 8200 only emits 2 forms of video on its SUBDB15 connector which are VGA (RGBHV) or YPbPr (component video) you can't take that and connect it directly to Scart. It would be good to know what you are going to connect it to, but I would recommend using the YPbPr output through the VGA port, they sell cables made for that and if you need Scart, look for a way to combine horizontal and vertical synchronies (RetroRGB shared a passive circuit a few weeks ago is easy to build and works well in most cases) or you use a YPbPr to Scart converter, Retrotink has options for this.
3) Let's see it is not completely necessary but in some cases where the sync is combined with some other signal such as Sync on composite or sync on Luma, it helps to clean the signal and thus have a clearer signal, although in my experience if your cables RGB are well built and end correctly at 75 Ohm is no longer necessary.

[lyzanxia]

Just did the clock generator mod...wow! what a difference (use it with my amiga's).
Before I had to fiddle with the horizontal and vertical adjustments, now with the external clockgen = perfect!!
Have not adjusted a thing and image is perfect centered every time and no tearing anymore in demos.

In my opinion this is a must do mod.

Thanks Rama!

[mutmut02]

@mutmut02 I can answer the easy question. Yes you can short the pins in any fashion you like as long as it creates continuity.

OK thanks, I do not have a jumper at hand and I don't see myself using the original version of the GBS firmware in the future so it makes sense for me to bridge it permantly.

Hi, I give you some answers based on my experience, I hope someone else can complement them.

1) I do not quite understand what you mean at this point since joining the dots with excess wire of a resistance is just what is recommended, see the RetroRGB video for more reference in this regard.
2) The GBS 8200 only emits 2 forms of video on its SUBDB15 connector which are VGA (RGBHV) or YPbPr (component video) you can't take that and connect it directly to Scart. It would be good to know what you are going to connect it to, but I would recommend using the YPbPr output through the VGA port, they sell cables made for that and if you need Scart, look for a way to combine horizontal and vertical synchronies (RetroRGB shared a passive circuit a few weeks ago is easy to build and works well in most cases) or you use a YPbPr to Scart converter, Retrotink has options for this.
3) Let's see it is not completely necessary but in some cases where the sync is combined with some other signal such as Sync on composite or sync on Luma, it helps to clean the signal and thus have a clearer signal, although in my experience if your cables RGB are well built and end correctly at 75 Ohm is no longer necessary.

1/ I'm talking about the jumper on the right hand side (facing the inputs) that bridges the two dupont pins.

2/ It was my understanding that GBSC could output 15 Khz RGBS through the Dsub 15 output. I want to use this to downscale my Xbox 360 (connect through VGA at 480p) and output this to scart consumer CRTs (I live in Europe).

3/ OK so I'll do without a sync stripper then, makes it quite easier.

Final (hopefully) question for the moment : should I wire each R-G-B wire's individual ground in my Dsub 15 -> Scart output cable ?

[Shiver_169]

1/ I'm talking about the jumper on the right hand side (facing the inputs) that bridges the two dupont pins.

2/ It was my understanding that GBSC could output 15 Khz RGBS through the Dsub 15 output. I want to use this to downscale my Xbox 360 (connect through VGA at 480p) and output this to scart consumer CRTs (I live in Europe).

3/ OK so I'll do without a sync stripper then, makes it quite easier.

Final (hopefully) question for the moment : should I wire each R-G-B wire's individual ground in my Dsub 15 -> Scart output cable ?

1) Ok, I already understand what you mean exactly as they already told you if this is going to be permanent, do the bridge with solder or cable without more.
2) The GBS 8200 can perfectly do the Downscale work from 480p to 240p but it doesn't output RGBS it outputs RGBHV at 15 Khz or YPbPr via VGA port.
And for your additional question I comment once again that it is not convenient to connect a Scart to the VGA output since there is only RGBHV and if you connect Scart you can damage your equipment. Or you combine horizontal and vertical sync in one with Bob's retroRGB circuit or you do transcoding the video to RGBS there are no more.

[EmKIronFist]

2/ It was my understanding that GBSC could output 15 Khz RGBS through the Dsub 15 output. I want to use this to downscale my Xbox 360 (connect through VGA at 480p) and output this to scart consumer CRTs (I live in Europe).

It's actually 15 Khz RGBHV, so you'll need a sync combiner in some form to make it RGBs. The circuit Bob posted on RetroRGB is pretty simple to make, so I recommend incorporating that into your SCART output. It also has the right attenuating resistors to behave appropriately with the 75 ohm sync termination of your TV.

Final (hopefully) question for the moment : should I wire each R-G-B wire's individual ground in my Dsub 15 -> Scart output cable ?

They're already tied together on the board, so it's basically up to preference. Just wiring one of the RGB grounds should be sufficient.

[SuperSpongo]

Also, don't forget that your TV needs a blanking voltage to switch to RGB.

[Josh128]

So, I wanted to revisit chaining the GBS w/ rama firmware to OSSC, for a specific use case.

Playing Neo Geo MVS on a Retrotek supegun (yes its cheap, but it works...pretty well)->SCART->OSSC, I optimized the OSSC, got it looking great, but would get infrequent momentary audio drop-outs. The MVS is known to need a bit of extra tuning w/ OSSC via 'H-PLL Post Coast' and 'HSync tolerance' tweaks. I'm attributing it to either a related tolerance mis-match, or something else unknown that isn't quite aligned with the MVS' output.

So, I tested the chain of:
MVS 1-slot -> Retrotek Supergun SCART output -> GBS-8200 w/ rama firmware, VGA output -> VGA-to-YPbPr transcoder -> OSSC YPbPr input

The GBS is set to 1280x1024 output, so OSSC is treating it as pass-thru.

I tested:
1) OSSC @ default settings, with minor tweaks to H. Backporch and V. Backporch to center the image
2) OSSC w/ attempted optimization

In the capture, the image ratio appears to be about comparable between both settings. On my flat panel, the optimized image is more compressed, much closer to what I assume is native 1280x1024.

Either way, it looks pretty darn good, and most importantly, no audio drop out.

And there was some recent questions about chaining GBS w/ rama firmware -> OSSC, so hear you go:
https://youtu.be/XAmvp0XqhoE

And here's a direct download link of the original video file: https://we.tl/t-4H5blxp2HD

The option you present is very interesting, but tell me what would be gained by chaining these 2 devices? I would think that the correct order would be OSSC and then GBS Control, especially for cases like SNES where framerate is a problem for many TVs and I think that with GBS Control this could be improved. And I have not wanted to buy an OSSC given its compatibility problems in resolution and framerate with many TVs on the market. And changed a little the subject you can pass us photos and model of your transcoder from VGA to YPbPr, I am looking for one for Dreamcast since VGA is quite problematic in my Setup it is the only console with this output and it is a problem for me.

Am I missing something here? This video is Street Fighter EX2, not 1 slot Neo Geo MVS.

[NoAffinity]

Haha, I guess that is pretty confusing. Admittedly I got sidetracked once I got deeper into testing and seeing how good it could look. The video became more about how good gbs->ossc can look without and with ossc optimization, which was meant to address an earlier question about whether gbs->ossc could work at all. But I see that is certainly not clear from the final product. Guess I'll need to do a supplementary neo geo video.

Sent from my SM-G955U using Tapatalk

[mutmut02]

Or you combine horizontal and vertical sync in one with Bob's retroRGB circuit or you do transcoding the video to RGBS there are no more.

I'm going to do this, thank you.

It's actually 15 Khz RGBHV, so you'll need a sync combiner in some form to make it RGBs. The circuit Bob posted on RetroRGB is pretty simple to make, so I recommend incorporating that into your SCART output. It also has the right attenuating resistors to behave appropriately with the 75 ohm sync termination of your TV.

I'll try it, thanks for the info.

[kitty666cats]

Think adding a 1024x768 'XGA' resolution is in the realm of possibility / some other 4:3 resolutions? For the CRT presentation monitor crowd

Not a particularly big deal b/c of being able to adjust 720p via GBS Control AND via menus/remotes on said types of monitor (or at least all the ones I've ever seen), but it could be cool

[maxtherabbit]

I have a feature request: support for EGA 350 line mode (21.8kHz)

Tried it with both HV and C-sync but no go, the 200 line mode (15kHz) works fine with C-sync

[rootbeer666]

I've had my GBS-8200 for a few years but I rather disliked it out of the box. I was excited to built GBS Control for it, and use rama's firmware.

First impression is a massive improvement, but I do see an annoying image problem that I haven't yet figured out how to correct. I have tested this with my NTSC Amiga 1200 (with the correct NTSC crystal oscillator), and I see a slow, bright sweep across the screen image. The source of this problem is apparently the fact that the input and output are out of sync. GBS Control detects input as 59.824Hz vertical refresh, but the output as automatically set as 59.829Hz. The slight vertical refresh difference is what causes the bright sweep crawl across the screen. I haven't found a way to lock the output to be exactly as the input vertical refresh. Adjusting HTotal makes the bright sweep more rapid, turning it into flicker, as the frequency difference grows, but I wasn't able to make them same and have that effect go away.

How do I get input and output to be in sync (vertically)?

Feature question, is it possible for this board to do frame doubling, to turn 50Hz into 100Hz or 60Hz into 120Hz refresh. My eyes are very sensitive to CRT flicker (always were).

Also, does the presence of the 3 RGB trimmers affect image brightness? Will the image get brighter if I remove them and solder in jumpers?

[RoboArmy]

*snip*

[maxtherabbit]

I have a feature request: support for EGA 350 line mode (21.8kHz)

Tried it with both HV and C-sync but no go, the 200 line mode (15kHz) works fine with C-sync

Ok update on this

I inverted the polarity of my c-sync signal coming from the sync combiner and now GBS-C will lock to the EGA 350 line mode and correctly identify it as medium res!


However the picture is still not being sampled/scaled correctly and messing with the picture controls don't solve the problem.

Rama I'd love to provide anything you could use to help debug this




this is what the title card is meant to look like:

[ulfrinn]

So the GBS-8220 with two VGA ports is the same exact scaler and works the same with GBS-C software? I ask this because I also noticed the 8220 has the second I2C headers installed. Someone without soldering skills could buy that board, and an arduino with pre-installed headers, some jumper wires, and not really need to solder anything.

[EmKIronFist]

So the GBS-8220 with two VGA ports is the same exact scaler and works the same with GBS-C software? I ask this because I also noticed the 8220 has the second I2C headers installed. Someone without soldering skills could buy that board, and an arduino with pre-installed headers, some jumper wires, and not really need to solder anything.

It's really not ideal, the 8220 is notoriously noisier and requires a little more modification just to get up to the quality of most 8200 boards. Some people have done what you describe and I suppose it's fine if you don't mind the noise and don't care about tearing, but when the basic solder work is so easy, going this route seems like more trouble rather than less.

I know the average person is very averse to soldering but if they're determined to take shortcuts, I think the solderless kits being worked on will probably be the better bet.

[rootbeer666]

I solved my flickering problem with clock generator installation as my input and output refreshes weren't quite lined up. The result is close to perfect now.

Now for the feature add question, can this chip do framedoubling? Display a frame twice to go from 50/60Hz to 100/120Hz vertical refresh (720x480 mode).

[lyzanxia]

Yes, as I also said: for amiga the clockgen is a must

Just did the clock generator mod...wow! what a difference (use it with my amiga's).
Before I had to fiddle with the horizontal and vertical adjustments, now with the external clockgen = perfect!!
Have not adjusted a thing and image is perfect centered every time and no tearing anymore in demos.

In my opinion this is a must do mod.

Thanks Rama!

[Shiver_169]

Hi guys, I would like your help and opinion with some issues.

1) To start I would like to know what configuration do you use to scale GBC / GBA games in the best way through a Gamecube with Gameboy Player? I use a Gamecube with Carby HDMI, I pass it through an HDMI to component video converter (for best results I use GBI and force the video to 240p) and from there to the GBS Control with 720p presets and I adjust the scale by hand from there as much as possible before obtaining distortions. But I think I am not doing it correctly since despite maintaining the correct aspect ratio in 3: 2 for the GBA some games show distortion when they do horizontal scrolling what they call shimering, someone could guide me on how its configuration does it which leads me to wonder if scaling would be better with the installation of the clock generator as it would not cause distortions.

2) For the second topic I would like you to provide me with a guide for the installation of the clock generator, preferably written or video, I see that many have already installed it but I still do not have much idea of ​​how to lifted the leg of the integrated without damaging it and some other points. And it is that for the majority of the reviews for the GBS Control that already find on the network even the recent one by Bob from RetroRGB do not mention anything regarding the installation of this add-on and I would like to be able to improve even more the magnificent setup of GBS Control with it.

I hope you can help me guys. I send greetings to all of you in these difficult times.

[rootbeer666]

Hi guys, I would like your help and opinion with some issues.

1) To start I would like to know what configuration do you use to scale GBC / GBA games in the best way through a Gamecube with Gameboy Player? I use a Gamecube with Carby HDMI, I pass it through an HDMI to component video converter (for best results I use GBI and force the video to 240p) and from there to the GBS Control with 720p presets and I adjust the scale by hand from there as much as possible before obtaining distortions. But I think I am not doing it correctly since despite maintaining the correct aspect ratio in 3: 2 for the GBA some games show distortion when they do horizontal scrolling what they call shimering, someone could guide me on how its configuration does it which leads me to wonder if scaling would be better with the installation of the clock generator as it would not cause distortions.

2) For the second topic I would like you to provide me with a guide for the installation of the clock generator, preferably written or video, I see that many have already installed it but I still do not have much idea of ​​how to lifted the leg of the integrated without damaging it and some other points. And it is that for the majority of the reviews for the GBS Control that already find on the network even the recent one by Bob from RetroRGB do not mention anything regarding the installation of this add-on and I would like to be able to improve even more the magnificent setup of GBS Control with it.

I hope you can help me guys. I send greetings to all of you in these difficult times.

To be honest you can see everything you need to see in the photo provided here:
https://github.com/ramapcsx2/gbs-contro ... tall-notes

Per this post here:
viewtopic.php?p=1396532#p1396532

You can read that you don't have to lift pin 40 for this mod. Because this is a corner pin, you can solder to the side of it, that's what I did. What I did is I stuck my clock generator board to the heatsink with double sided tape, I had left over resistor leads that were cut, so I soldered the resistor lead to the CLK0 pad first, then bent the lead down toward pin 40, clipped the lead to length, then bent to close to the side of pin 40, and just neatly soldered it.

[NoAffinity]

This 3m tape also works well for securing the clock gen board as well as the esp:

https://www.amazon.com/dp/B007Y7E0CQ/re ... jFb73S28E2

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