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First post, by scorp

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Hello there,

just wanted to briefly introduce another small project of my - a MCE-Adapter. You can use it to connect old PCs to a 15kHz capable RGB/VGA Monitor or to use it with Sync converters like GBS-8200. I made it to be able to use my Hercules, CGA and EGA graphics cards, but may be someone else will find it useful as well. The project is completely open source, both hardware and software.

Features:
- Converts digital MDA, Hercules, CGA, low-res EGA, high-res EGA to analog RGBS or RGBHV/VGA signal
- Color DAC for 3, 4, 16 and 64 color modes
- Switchable composite sync from H- and V-Sync
- Loop through HV-Sync, colors conversion only mode
- Switchable composite sync inversion
- Includes IBM's "brown-hack"for CGA and 16-colors EGA modes
- Switchable green and white monochrome screen emulation

You can find the project here:
https://github.com/necroware/mce-adapter

I also made a video series about it on my youtube channel, if you are interested:
https://www.youtube.com/watch?v=7c3yLX52ZEs&l … uGk6_uk54765G1t

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My Youtube channel Necroware

Reply 2 of 42, by Jo22

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Cool! 😎

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 42, by keropi

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How does it handle the EGA 640x350 mode? what is the output?
looking good ofcourse!

🎵 PCMIDI mpu site buy+info
🎧 WIP Orpheus soundcard site
💻 WTB Amstrad PC7486SLC-33 system

Reply 4 of 42, by weedeewee

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keropi wrote on 2021-02-08, 14:18:

How does it handle the EGA 640x350 mode? what is the output?
looking good ofcourse!

https://www.youtube.com/watch?v=F1685u-QQ0k

Check out his videos.

What I want to know is, where do I buy one ? 🤪

Reply 5 of 42, by scorp

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keropi wrote on 2021-02-08, 14:18:

How does it handle the EGA 640x350 mode? what is the output?
looking good ofcourse!

Hi, as I wrote it can handle hi-res 64-colors EGA. The output is always analog RGBS or RGBHV, dependent on jumpers. Just watch my video series about it, they are not too long, but you can find a lot of details there.

My Youtube channel Necroware

Reply 6 of 42, by scorp

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weedeewee wrote on 2021-02-08, 14:20:
https://www.youtube.com/watch?v=F1685u-QQ0k […]
Show full quote
keropi wrote on 2021-02-08, 14:18:

How does it handle the EGA 640x350 mode? what is the output?
looking good ofcourse!

https://www.youtube.com/watch?v=F1685u-QQ0k

Check out his videos.

What I want to know is, where do I buy one ? 🤪

I didn't plan to sell them, but if you are interested, you can buy one from me. I have some left after this project. However, it depends where you live, since the shipment could cost more, than the adapter itself 😁

My Youtube channel Necroware

Reply 9 of 42, by keropi

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weedeewee wrote on 2021-02-08, 15:01:
keropi wrote on 2021-02-08, 14:55:

ah I missed the part where the GBS-8200 is needed 😁

you also missed the part where it is not needed 🤪

not needed for the 25k 640x350 ega mode?

🎵 PCMIDI mpu site buy+info
🎧 WIP Orpheus soundcard site
💻 WTB Amstrad PC7486SLC-33 system

Reply 10 of 42, by weedeewee

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keropi wrote on 2021-02-08, 15:57:

not needed for the 25k 640x350 ega mode?

https://youtu.be/F1685u-QQ0k?t=873
Not needed if your monitor supports the frequencies 😁

Reply 11 of 42, by scorp

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Yes, you need GBS-8200 or similar device only, if you need to convert the frequencies. If you have a 15-25kHz capable monitor or a TV with SCART, you don't need anything else, but this adapter to get MDA,CGA,EGA onto the screen.

My Youtube channel Necroware

Reply 12 of 42, by maxtherabbit

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analog displays that will sync to 22kHz for EGA are extremely rare - tri sync arcade monitors and the original NEC multisyncs and not much else

Reply 13 of 42, by weedeewee

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maxtherabbit wrote on 2021-02-08, 18:18:

analog displays that will sync to 22kHz for EGA are extremely rare - tri sync arcade monitors and the original NEC multisyncs and not much else

I always wonder why that is, when you see vga monitors do 15kHz on one resolution and 30kHz, 40kHz and higher on others.

Reply 14 of 42, by imi

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well, the sync frequency scales with resolution (and refresh rate) obviously ^^

(though there's a lot more to it with different overscan rates and/or line doubling in different modes)

Reply 15 of 42, by scorp

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maxtherabbit wrote on 2021-02-08, 18:18:

analog displays that will sync to 22kHz for EGA are extremely rare - tri sync arcade monitors and the original NEC multisyncs and not much else

There are at least Benq Monitors, which should support everything between 15 and 31kHz (and above). If I remember right the models were BL702, BL902 and BL912. However, I think, that the list is longer, than you think, but I can't prove it, since I have only NEC Multisync here. Which by the ways easy to get, I bought two used 1970NX for 10€ each, just couple of weeks ago.

EDIT: At least the list of known 15kHz capable monitors is quite long, I'm wondering how many of them do also support frequencies between 15 and 31kHz.... (see http://15khz.wikidot.com/)

My Youtube channel Necroware

Reply 16 of 42, by weedeewee

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You know, another odd thing, I think, is that all those LCD monitors should easily be able to handle those low frequencies, yet somehow do not.
I've noticed that some driverchips (VGA,DVI,HDMI->LVDS) seem to have an extra eeprom for things like the menu and wonder if somewhere in that code there's software limits being placed on the hardware itself.

Reply 17 of 42, by scorp

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Can't tell that, but at least GBS-8200 is strictly limited to 15kHz and everything beyond that sync doesn't work. Rumors say, that this is not the limitation of the used chip, but of the software. However gbs-control tried to get to other frequencies with mediocre success, as you probably saw in my video. I didn't get into the code of gbs-controll (yet), but I hope there is more improvement possible in that direction.... Well, my adapter is quite helpful for people who have a monitor with lower sync frequency support, or a RGBS CRT, like they were used for Amiga and such things. If you just want to use any VGA monitor, you probably have to take much more money in the hand and by the MCE2VGA adapter mentioned above. However it costs 10 time more, than what I made. I guess, it depends on what you are going to do and at least for my use case it was a perfect solution. Now I can directly use MDA, Hercules, CGA and all kinds of EGA with my monitor with zero latency. Btw, the VGA to HDMI adapter, which I mentioned in my video, supports also 18kHz and above. Unfortunately, it can't handle 15kHz, but that would be too awesome....

P.S. I forgot to mention my 15" EIZO L365, which you also can see in some of my other videos. It also supports 24kHz, but not lower.

My Youtube channel Necroware

Reply 18 of 42, by weedeewee

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scorp wrote on 2021-02-08, 20:58:

Can't tell that, but at least GBS-8200 is strictly limited to 15kHz and everything beyond that sync doesn't work. Rumors say, that this is not the limitation of the used chip, but of the software.
...
P.S. I forgot to mention my 15" EIZO L365, which you also can see in some of my other videos. It also supports 24kHz, but not lower.

When I first became aware of the GBS8200 I looked into the chip that is supposedly used on the board, TrueviewTM5725 http://file.yizimg.com/420856/2013041613555642.pdf

Clock-recovery CircuitProgrammable phase adjustment cellsHSYNC frequency range is from15KHz to 110KHz

So maybe it's the board design, maybe it's a different chip version/revision, but according to the pdf it should definitly be able to handle a much larger range than just 15 to slight bit over 22.

and I recall there were some powersupply issues with the board which cause performance issues.

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Reply 19 of 42, by scorp

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Hehe, there were full bunch of issues with that board. It's a tinkerer heaven 😁 On gbs-control project site is a wiki with a list of suggestions, how to improve the situation... Still, I found it quite exciting making this project, I learned a bunch of things and could try out a lot of stuff, which I knew in theory.....

My Youtube channel Necroware