Thank you very much! ^^ I've never heard of this utility before.
Just found out its name means "green" in English, also. Cool. 😎
It's really useful, I think - back in the day, a lot of people had monochrome CGA, actually.
Some reasons why:
a) CGA's colour palette was eye straining 😉
b) because monochrome video monitors were affordable and provided good video quality
c) because foreign monitors didn't decode CGA's NTSC signal.
d) because most PC clones had a monochrome video output on their RCA/Cinch connector (no colour burst circuitry)
Ok, technically, PAL<->NTSC transcoder chips existed in the 1980s.
But they were rather rare and didn't convert the sync rates 50 Hz / 60 Hz, just the colour encoding.
PAL/SECAM video monitors, on the other hand, could display 60 Hz video directly in monochrome, if adjusted (V-Hold or H-Hold knobs).
Some games even used the brightness levels of the four CGA colours as matching shades of gray.
@Tiido Thanks for the explanation, too.
There's an alternative to a 15-31 KHz monitor, too.
Converters exist which convert an 15KHz CGA/EGA signal to 31,5KHz VGA (CGA2VGA ?).
At least timing-wise, they're compatible with real CGA/EGA.
They may not accept TTL signals, since they were made for analog RGB (like Commodore 128), rather than digital RGBI.
However, it may still indirectly work, partly, if the TTL signals overdrive the inputs (full on instead of various intensity levels) - at cost of of a few colours.
So ideally, another adapter/converter might be needed here.
To get scan lines, another device is sadly needed, though. Say, SLG3000. 🙁
And maybe a sync stripper is needed, too. 🙁
..
Then, there's a passive VGA adapter which converts colour VGA to monochrome.
It's sending a monochrome picture to one of the individual R/G/B lines.
https://blog.tindie.com/2022/05/monochrome-vg … -color-schemes/
VGA can do create a monochrome conversion of colour on its own.
Not sure if the adapter is using a VGA cards's pin12 for that purpose (pin12= the monochrome monitor detection). 🤷♂️
Same could be done with a VGA to SCART cable, I guess.
VGA's CRTC can be configured for 15 KHz video.
https://www.geocities.ws/podernixie/htpc/cables-en.html
Edit: Text removed. I was a bit confused.
"Sync on Green" maybe is an issue if we want to use CVBS/Composite signals for an all green image.
A VGA DIY cable can provide a pure monochrome signal, however, by contrast.
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Also, there are VGA cards which have a 9pin TTL port next to 15pin VGA.
They can be used as a substitute to a real CGA or EGA card, if really needed. (Except Composite CGA)
Since most early VGA cards (Trident 8900, Paradise, OAK etc) have software-controlled emulation modes for CGA, EGA or Hercules built-in, this should work.
The DIP switch used to select the monitor type should activate the corresponding emulation mode - if no VGA or Multisync monitor is selected.
..
The nice thing about EGA is its close relationship to VGA, I think. Or vice versa.
In mode 12h (640x480 Standard VGA), VGA uses the same 16 colours as EGA by default, for example.
Both EGA and VGA have their own video BIOS, too.
Their control ports are similar, AFAIK.
- That's one big difference to CGA also, I suppose. It has different ones.
Maybe that's another reason why VERDE can instruct the VGA card to alter the CGA image.
(AFAIK, EGA/VGA can also listen to CGA ports for compatibility reasons, though some commands are ignored. Also due the lack of a real Motorola CRTC. Edit: Emulation mode excepted, it can simulate the Motorola CRTC partially)
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