Best GBS 8200 MOD for the Amiga computers

[amigappc]

I am thinking of getting Gonbes board to connect Amiga to VGA monitor.

Can someone tell me what is the best MOD for picture quality I can do with it?

Is there any certain board revision I have to search for?

I was watching this video yesterday, seems like OK mod:

[ Show youtube player ]

[rabidgerry]

I can't speak for what revision you should go for. I know I have the GBS8220 and by itself it was usable and a step up from my dying composite output.

But the mod in this video basically allows you to install a custom firmware called GBS Control. Eventually you will end up with the firmware installed and be able to control all the settings via your smartphone using a GUI accessed via an ip address.

The firmware improves the picture quality by about 100%. It is night and day.

Get this mod done and you are sorted!

There are a couple more which I will share later on. One I have conflicting specification on which parts I should buy in order to complete it successfully.

[amigappc]

I think he used this guide:
https://github.com/ramapcsx2/gbs-con...d-the-Hardware

Another video:
[ Show youtube player ]

However I can see that someone reported screen tearing on Amiga 500:

https://github.com/ramapcsx2/gbs-control/issues/104

This really seems like good and cheap enough option, I really would like to hear experiences if there are any, for the Amiga usage.

[rabidgerry]

Well there is options to stop screen tearing if you get it. I can't comment on A500 issues as I have a 1200 but there are so many improvement options to eliminate these problems.

I use the GBS8220 with GBS control currently btw.

Yes that is the guide I followed also and allowed me to create my own arduino board loaded with GBS Control firmware.

It is lag free but I don't know if I get a smearing effect sometimes with my display simply because of the monitor I am using. I can't quite work out what is the cause. It's when some screens scroll the background will look kind of distorted. One game I noticed this on is Torvak the Warrior. With Doom though I don't get anything like this. F1GP I don't get anything like this either. Other people haven't mentioned this issue I see with certain games so may be it is my monitor.

I think the picture quality generally is really good, it easily brings the device up to the level of something that is 4x the price in my opinion.

[rabidgerry]

other mods (one of which I still intend to do but like I mentioned don't know the exact parts I need)

https://github.com/ramapcsx2/gbs-con...re-Mod-Library

[amigappc]

One more question.

when I look at this install guide:
https://banfi.co.uk/blog/?cat=28

I can see he is using 680 ohm resistor on Sync signal.

Did you use it as well?

[amigappc]

Originally Posted by rabidgerry

other mods (one of which I still intend to do but like I mentioned don't know the exact parts I need)

https://github.com/ramapcsx2/gbs-con...re-Mod-Library

Which mode exactly?

And why do you think it is needed?

[rabidgerry]

This mod

https://github.com/ramapcsx2/gbs-con...-8200-Variants

and for the reasons mentioned there also. Scroll down to the GBS 8220 bit for the mod I mean. I have a video where a guy does it also but I have to look for it first.

One more question.

when I look at this install guide:
https://banfi.co.uk/blog/?cat=28

I can see he is using 680 ohm resistor on Sync signal.

Did you use it as well?

Yes I did.

[rabidgerry]

Here is the other video.

The part I question is the values of the caps because the guy links to the wrong values in the description below so that makes me ask "well what values should I be using?"

[ Show youtube player ]

[Higgy]

To stop tearing there is a ClockMod. It uses a cheap ebay part.
The only problem is if using a PC monitor it needs to accept 50Hz. My PC CRTs are ok but most of my LCD can't do this.
So it is ok for my 50/60Hz modified consoles but will not work on AMIGA.

[rabidgerry]

Originally Posted by Higgy

To stop tearing there is a ClockMod. It uses a cheap ebay part.
The only problem is if using a PC monitor it needs to accept 50Hz. My PC CRTs are ok but most of my LCD can't do this.
So it is ok for my 50/60Hz modified consoles but will not work on AMIGA.

Are you sure?

GBS Control has 50hz and 60hz modes so it doesn't matter what your monitor is.

Also my understanding of the clock mod has nothing to do with screen tearing, it's to do with stable image synchronisation for say monitors or tvs that have the image bounce about the screen before settling or for those that don't even settle at all. I see it does mention about tearing here https://github.com/ramapcsx2/gbs-con...-install-notes but there are already controls to stop tearing with the firmware.

Rama the guy behind these mods also told me another way for better syncing was to use a VGA to HDMI adapter which also provided better syncing.

However I wouldn't implement any of these unless you found you couldn't get a stable image. My TV flits about the screen for a bit sometimes, but after I saved custom presets using the GBS Control I found it stabilized once I had tailored settings to me liking, stabilizes like within half a second now. On my NEC monitor which actually accepts native amiga rgb output but cuts off the bottom a bit it syncs immediately.

[Higgy]

My understanding is that the mod matches the correct sync of the input signal. So as Rama told me you can't force it to be 60Hz if your feeding in a 50hz signal, that is the whole point of the mod to get the exact frequency.

[amigappc]

Can you provide me details about clock mod? Link, description? Is that something extra or works in conjunction with gbs-control?

In short, what are needed mods to make Amiga picture as best as possible on CRT or LCD monitors?

Originally Posted by Higgy

To stop tearing there is a ClockMod. It uses a cheap ebay part.
The only problem is if using a PC monitor it needs to accept 50Hz. My PC CRTs are ok but most of my LCD can't do this.
So it is ok for my 50/60Hz modified consoles but will not work on AMIGA.

[amigappc]

Also, can this GBS 8200 accept chroma/luma (s-Video) signal form Commodore 64 and upscale it to VGA?

[amigappc]

And which board revision to search for? I see there are v40, v3.0, v5.1 on Aliexpress

[Higgy]

https://github.com/ramapcsx2/gbs-control

This has everything.
Clock mod is part of GBS Control. If it is installed it will just work.
Sorry pretty sure no Composite or S Video. Just RGB in. It might accept Component. I think my Wii, Xbox and PS2 might do that, but never tested.

[amigappc]

Thanks. Any particular board revision needed?

Originally Posted by Higgy

https://github.com/ramapcsx2/gbs-control

This has everything.
Clock mod is part of GBS Control. If it is installed it will just work.
Sorry pretty sure no Composite or S Video. Just RGB in. It might accept Component. I think my Wii, Xbox and PS2 might do that, but never tested.

[rabidgerry]

Originally Posted by amigappc

Thanks. Any particular board revision needed?

No. If you bother to read the links that have been posted already it discusses the variant in the boards and the mods. Most mods are made redundant by GBS control so all you really need to do is that and then if you find you need to clock mod go ahead and do that.

Why don't you watch the video link I posted earlier. It goes through all this and all the mods and is easier to follow than just reading the instructions of the website like I did.

Originally Posted by Higgy

My understanding is that the mod matches the correct sync of the input signal. So as Rama told me you can't force it to be 60Hz if your feeding in a 50hz signal, that is the whole point of the mod to get the exact frequency.

So the clock mod is for sync and tearing (and not always needed otherwise everyone who has one would do the mod) ok I got that. Rama did suggest it to me for unstable picture before. I asked him earlier about the clock mod and he referred to tearing line which I don't get really using Active FrameTime Lock and using the first method.

But I don't know what you mean about only outputting 50mhz.

Are you saying that if I was to do the clock mod then I would only be able to output 50mhz to match what is coming in from the Amiga??? I wouldn't bother in that case unless I really had tearing issues.

Currently using the GBSC I can output both 50 and 60.

If that is what you are suggesting then that makes sense.

I have a CRT that doesn't accept my native Amiga RGB output and the only way I can get anything on screen is by using he GBS board outputting 60mhz.

If I was amigappc I would not touch the clock mod until I saw how things were and how the onboard Active Frametime lock option worked out to begin with. Any tearing I experienced I got rid off using that.

[Higgy]

Hi.
Although the GBS-Control mods are quite tricky, I guess there is no way around lifting a pin on a chip to do the ClockMod so people might not be comfortable doing that.

If the hardware outputs a 50Hz signal, something extra will be required to get it to 60Hz. The difference between 50 and 60 could show as shimmering/tearing etc.

The ClockMod is locking the (VGA) output to the RGB input, so it has to be the same as the input. If you output 60Hz on the AMIGA (say NTSC) then the ClockMod will adjust to 60Hz.

The CRT won't accept the AMIGA signal because the AMIGA outputs 15KHz Vertical signal. PC monitors expect 30KHz Vertical.
The GBS will be 'scandoubling' the RGB signal to a VGA compatible 30KHz Vertical signal.
I think it is because you are doubling a signal (15-30KHz) that is fine, but to go from 50Hz-60Hz it is not a clean multiple so there will have to be some slight mismatch.

It hope the info helps. There is Horizontal freq and Vertical freq, KHz and Hz. Rama is the man when it comes to answers. Yeah recomend start off with basic mods and work your way up if needed.

[rabidgerry]

Originally Posted by Higgy

Hi.
Although the GBS-Control mods are quite tricky, I guess there is no way around lifting a pin on a chip to do the ClockMod so people might not be comfortable doing that.

If the hardware outputs a 50Hz signal, something extra will be required to get it to 60Hz. The difference between 50 and 60 could show as shimmering/tearing etc.

The ClockMod is locking the (VGA) output to the RGB input, so it has to be the same as the input. If you output 60Hz on the AMIGA (say NTSC) then the ClockMod will adjust to 60Hz.

The CRT won't accept the AMIGA signal because the AMIGA outputs 15KHz Vertical signal. PC monitors expect 30KHz Vertical.
The GBS will be 'scandoubling' the RGB signal to a VGA compatible 30KHz Vertical signal.
I think it is because you are doubling a signal (15-30KHz) that is fine, but to go from 50Hz-60Hz it is not a clean multiple so there will have to be some slight mismatch.

It hope the info helps. There is Horizontal freq and Vertical freq, KHz and Hz. Rama is the man when it comes to answers. Yeah recomend start off with basic mods and work your way up if needed.

It does indeed help!

Well I found it weird about the CRT I own. It's from the 90's. I figured surely a CRT from then would sync down to 15khz but what do you know I was wrong! Someone suggested trying the VGA only driver in workbench but I dunno how to use it. Think it needs loaded up within my startup sequence as opposed to just sticking in the monitor drivers folder.

When I was first made aware of the clock mod the pin lifting was being done.

As I found out yesterday, the pin 40 is no longer required to be lifted. It didn't need to in the beginning actually it was just done to make things handier apparently. I asked about this yesterday as the install guide mentions nothing about pin lifting yet when I first read about the mod say 8 months ago lifting pin 40 was a step. Now it seems you just solder a wire from pin40 to one of the pads on the clock pcb. For my skill level of modding it's perfectly within reach (no expert but have done my fair share with an iron over the years) but I might not bother.

Here is the clock mod install

https://github.com/ramapcsx2/gbs-con...-install-notes