GBS 8200/8220 CFW Project

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Iraito
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Re: GBS 8200/8220 CFW Project

Post by Iraito »

I still couldn't move the picture but i pressed RGBHV and the picture became perfectly centered, it's as if the GBS did an auto adjust.
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Nuck-TH
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Re: GBS 8200/8220 CFW Project

Post by Nuck-TH »

Okay, i decided to follow advice and use 720p for "big" scaling and 1080p for integer...
And immediately bumped into problems:
- hdmi adapter(recommended, based on FS9299 chip) for some reason takes very long time(~half a minute) to sync into 720p, other(1080p, x960) are shown immediately.
- right side of border mask get bumped further if i try to scale/move picture in 720p so i can't hide garbage/screen repeat there :(
edit: i managed by first centering whole image with HS move, then scaling, then narrowing the border. but if i try scale again - it will bump border again...
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Not sure why the adapter takes longer to lock to the signal.

Are you trying to scale down?
There is just a small margin to scale down before the mask has to move as well.
I don't know of a reliable way to calculate the needed positions on the fly, so you have to move the mask manually.

Scaling is not recommended anyway, as it misaligns horizontal pixels. It's better to choose a different preset.
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Nuck-TH
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Re: GBS 8200/8220 CFW Project

Post by Nuck-TH »

rama wrote:Not sure why the adapter takes longer to lock to the signal.

Are you trying to scale down?
There is just a small margin to scale down before the mask has to move as well.
I don't know of a reliable way to calculate the needed positions on the fly, so you have to move the mask manually.

Scaling is not recommended anyway, as it misaligns horizontal pixels. It's better to choose a different preset.
Anything i can try about long syncing?

It is(sega saturn bios again as reference) very stretched horizontally(almost to full width), so i'm trying to make aspect ratio correct. Vertical size is correct tho.
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

I'll look into the sync issue when I have some time.
I think it's to do with the HDMI dongle though, as they also run their own "operating system" and these can get confused when the input changes.
For example, I need to wait a few milliseconds before outputting sync on a mode change, else my HDMI dongle only displays black.

For the 720p preset, the stretching is how it's "supposed to be".
Users are meant to correct the aspect ratio on the display, if that's possible.
If the display doesn't allow this, a different preset should be used.
lyzanxia
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Re: GBS 8200/8220 CFW Project

Post by lyzanxia »

Just made 2 gbscontrol mods and loving them!

Have 2 questions though:

I seem to have some sort of bleed to the right, what could that be?
Tried contrast/brightness on my monitor but did not help. Any idea?

Image

Second question: I added the 100 ohm resistor between sync and ground on the gbs. Is the 680ohm to sync (as Ian Steadman suggests) still necessary? Or is it one or the other?

Thank you for this great mod!!!
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Aw man, I just switched my GBS8220 to a GBS8200 V4 (the common one) and immediately noticed that it kills my shiny new 1080p preset with jailbars :/
It looks like 1080p really is pushing it a bit too far.

I still hope a hardware mod can fix this.
It clearly works jailbar free on the 8220 (which uses an external video amplifier / buffer), so I'm suspecting the DAC is pulling too much, too noisy power.

Do you guys get this problem with the new 1080p preset?
It requires large single color surfaces to see, such as the 240p test suite menu background.
cryptblood1986
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Re: GBS 8200/8220 CFW Project

Post by cryptblood1986 »

rama wrote:Let's settle on 10uF for the large local storage caps, as more capacity seems to be at the upper end of current market offers.
We want as high a voltage rating as possible, but that increases size. We want to limit size to 0805, so they can still be soldered besides the 0605 stocks.
Ebay has some cheap listings for:
0805: 10V
0605: 6.3V
Actual voltages are 3.3V for the main supply (C23 C41 C48), and 1.8V for the digital supply (C42).
By the way, I just noticed that on some GBS board designs, C41 is more crowded. It can be replaced by C43.

The small SOG coupling caps of 1nF all come at voltage ratings much higher than required.
Here it's better to focus on size (0605 preferred, 0805 okay), and their material (NP0 / C0G preferred).
Interested in doing this but I don't exactly understand what to do. I tried searching for 0805 10v and 0605 6.3v but they are quite pricey where I life. I have some regular sized caps 22uF 16v. Am I supposed to replace the c23, c41, c48, and c42? How would I know which side is positive and which is negative? Image
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

Did some testing with an MD2 that produces very little jailbars (using csync)
all tests at stock 1080p except autogain, on a PC lcd monitor with VGA in and DVI in to an HDMI cable (shouldn't matter)

HDMI GBS : very little jailbars (probably the console) even on white screens
8200 v4.0 GBS : noticiable jailbars on flat colors and extreme interference-like jailbars on a white screen, interference is slighly reduced when displaying a grayer tone.
same GBS with VGA to HDMI box : very little jailbars, much like HDMI version (I get a greenish tint but it's most likely the converter being lousy). Even white screens are clean.

White screens on Sonic 1 / 2 "SEGA !" make this very apparent.
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AndehX
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Re: GBS 8200/8220 CFW Project

Post by AndehX »

My capture card doesn't support 1080p/60 but I have one that does on order, and I should get it next week, so I'll do some testing too.
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Thanks, testing is always appreciated!

For the 1080p preset, I've isolated the DAC power pins and those indeed have a huge effect on the picture.
This test also showed that the actual problem is with the memory timings, which I can fix :)
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Ryoandr: Could you check whether the interference stuff is fixed?
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

Interference is gone, but jailbars are still present, faint but noticiable on flat colors. Also tested on an SNES and same results (over VGA direct to monitor).
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Oki, thanks :)

The jailbars themselves appear to be a PCB issue.
Routing of power and ground is quite good for the price, but it's probably not good enough for 1080p.
The GBS8220 improves on this by using a dedicated video buffer, so maybe a hardware mod could help the 8200.

I noticed that just changing the VGA cable had some effect on the issue.
I haven't tested the HDMI dongle on this board yet, but maybe it's enough to fix it (by not requiring the DAC to drive a long cable).
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

some quick captures with HDMI version and 2 chip SNES
https://imgur.com/a/WXubr5q

jailbars definitively here, not terrible but noticiable. In lighter gray mostly
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AndehX
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Re: GBS 8200/8220 CFW Project

Post by AndehX »

Ryoandr wrote:some quick captures with HDMI version and 2 chip SNES
https://imgur.com/a/WXubr5q

jailbars definitively here, not terrible but noticiable. In lighter gray mostly
hot damn, the ghosting on the 2chip snes is hella bad, jesus
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

yeah, and then people wonder why 1chips are in demand :)
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AndehX
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Re: GBS 8200/8220 CFW Project

Post by AndehX »

Yeah, massive difference. This is my 1-chip with an RGB bypass installed (on the 720p preset):

Image

Image
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

rama wrote:Oki, thanks :)
I noticed that just changing the VGA cable had some effect on the issue.
I haven't tested the HDMI dongle on this board yet, but maybe it's enough to fix it (by not requiring the DAC to drive a long cable).
Confirmed that using a dongle avoids the jailbars.
I'm okay with this solution, as I expect lots of users that want 1080p also want this for their large TV and probably use an HDMI dongle to connect to it.
The dongles are $5 *and* they improve quality :)

3 chip SNES are just super blurry by default.
But some people are working on it ;p
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AndehX
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Re: GBS 8200/8220 CFW Project

Post by AndehX »

rama wrote:
rama wrote: 3 chip SNES are just super blurry by default.
But some people are working on it ;p
Seriously, once the 2 chip snes gets the RGB bypass it needs, the price of 1-chips will most likely drop.
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

The only working modification I know of will be expensive in parts and labour, unfortunately.
WIP thread here: viewtopic.php?f=6&t=64930
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

lyzanxia:
Bleed to the right like that is usually a sign of a non-ideal RGB cable, or even a weak DAC (within your Amiga).
It's something to be expected with really old hardware designs (I'd say *designed* earlier than maybe 1994).
You should compare your results with others that use this Amiga.

You should add the 680Ohm series resistor, yes.
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

Ryoandr wrote:Interference is gone, but jailbars are still present, faint but noticiable on flat colors. Also tested on an SNES and same results (over VGA direct to monitor).
Was this the result of a firmware update? I have interference on both my units, one is worse than the other but still a minor annoyance on both.

Sent from my SM-G955U using Tapatalk
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

Only over the newer 1080p preset and over VGA ; with the latest update there's still a bit of moving interference so you should not use 1080p over VGA. My experience is that if you use an HDMI variant or a dongle with a short cable you'll get the (very) faint jailbars (again, over 1080p only).
Iraito
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Re: GBS 8200/8220 CFW Project

Post by Iraito »

When playing on snes the picture is slightly framed, i know it's normal since on crt that part shouldn't be visible but how should i tackle the scaling on the GBS ? if i keep scaling the picture keeping the proportions given by the preset (720p) i get almost a perfect 4:3 ratio with barely 2 vertical black bars, should i just keep scaling the picture vertically and fill the 4:3 canvas ?

Example of the almost perfect 4:3 canvas https://www.youtube.com/watch?v=5V5HuuSVnTo
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Latest update brings down jailbars a little more. Somehow the (unused) 4th DAC channel doesn't like being disabled, so it's now enabled and fixed to 100% output.
I think this causes a slight current draw increase, which is somehow good against jailbars.

Also new: 640x480 presets use input oversampling like the other presets now.
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Iraito:
Gotta admit, aspect ratios aren't my strong suit.
It's actually a problem of having reliable references.
I can tune a preset so that circles are round on my display, only to see another display make them ovals.
I also need to consider what most displays are probably going to do, and also what most sources are doing.
For example, it doesn't help that many retro machines don't use all 240 NTSC lines, but more like 224 only.
They also have alternative display modes where they *do* use all lines.

So all I can recommend is that you tune for maximum viewing area while keeping circles round :)
Another tip: Many TVs can "overscan" or "zoom", which they often do without loss of quality.
Use this to fit a default preset to full screen. The scaling defaults in all presets are quality optimized, so if you can keep them, that's best.
Iraito
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Re: GBS 8200/8220 CFW Project

Post by Iraito »

Good to know, then i will scale the picture maintaining the aspect ratio given by the preset. After i finally switched to the professional PSU i can say that the GBS really produces clean and beautiful results, great project.
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AndehX
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Re: GBS 8200/8220 CFW Project

Post by AndehX »

here's a quick 1080p clip. No visable jailbars or interference. Looks brilliant!

https://youtu.be/B7dQPqsMXwA
rama
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Re: GBS 8200/8220 CFW Project

Post by rama »

Great, I think we really got lucky that there still existed workarounds and tweaks against jailbars.

For the next cool thing, I'm looking at this really interesting board :)
Image
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