I have a mid-1980s CRT monitor, a C. Itoh Chroma Pro CM1000, with an 8-pin DIN RGB input that's visually similar to the digital RGB input on a Commodore 1084. The input is selectable between "RGB," "RGBI," and "XRGB."

Presumably "RGBI" is an RGB + intensity digital signal, i.e., CGA. But what are "RGB" and "XRGB?"

I'm guessing that "RGB" is probably digital RGB but without the intensity signal, but I'm totally mystified about what "XRGB" might be.

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    I would expect ‘RGB’ to be analog RGB (with the intensity signal incorporated into the components). Going by <msx.org/wiki/RGB_(8-pin_DIN_45326)>, there were several incompatible pinout standards for 8-pin DIN RGB. I would presume the switch chooses between them. (I cannot vouch for any of this, though. Take it with a grain of salt.) However, I don’t see any resources about an RGBI pinout over 8-pin DIN. Is the switch and the 8-pin DIN socket all there is? Can you provide a photo? Aug 28 '21 at 18:03
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    Does your monitor have a name, such as brand or make and model number?
    – Justme
    Aug 28 '21 at 18:27
  • It's a C. Itoh Chroma Pro. Maybe XRGB is 2-bit RGB, i.e., EGA. Aug 28 '21 at 19:36
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    @WillisBlackburn Would you mind to incooperate the information into the question (and delete the misleading commodore reference)? Also, what is the exact type as Chroma Pro was a series of screens with several related screens. Adding a photo would help. And/or a description of each connector.
    – Raffzahn
    Aug 28 '21 at 22:16

The Chroma Pro was a series of screens introduced after 1985. I remember using a CM 2000 in the late 80s.

RGBI is essentially IBM CGA.

RGB is Analogue RGB.

I used both modes with IBM and an Atari ST.

XRGB in turn should be what Apple used to call the Apple III's digital video signal. It's a 4 bit TTL compatible digital port. See this pinout). The Extended 80-Column Text/AppleColor Adaptor Card (Manual) available for the Apple IIe (put in AUX slot) used the same output signal.

It was intended to be used with the Apple Monitor 100 (Manual), their first, Apple branded, colour screen. Beside that there was also at least one screen made by Taxan and, as I'd assume, the C.Itoh CM2000. Would fit time frame and technology quite well

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    Raffzahn forgot to mention one of his previous posts describing the meanings of the 16 possible colors of an Apple III. Aug 29 '21 at 9:55
  • Mine is a CM1000. I bought it on eBay so I don't actually have it yet, but I added a photo from the seller's listing. I'm kind of crossing my fingers that "RGB" is actually analog since that would make it a really useful all-around CRT. Aug 29 '21 at 14:03
  • @MartinRosenau Oh. I did not remember at all. Guess I'm simply writing way to much. Thanks.
    – Raffzahn
    Aug 29 '21 at 18:10
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    The monitor is now here. It looks pretty nice but I have no idea how to hook it up. I'll guess I'll just try different pinouts and see if anything works. I only have to get 3 pins right (green, H and V sync) to get a picture, and the input jack is an 8-pin DIN, so there are... 56 different 3-pin groups in the input jack, and 6 ways to hook up each one? So 336 different combinations? I suppose I could try them all. :-) Then figuring out red and blue would be simple. Sep 9 '21 at 23:18


From my reading of that post linked above, XRGB is a variation of RGB that maps to NTSC artifact colors, rather than the usual 16 seen with RGBI. This is likely related to the Apple 2 and IBM CGA 16 color artifact palette and monitor suitability for software written with artifact color in mind.

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