> > 1. Some sites talk about e.g. arcade graphics as being "analog CGA" -- I > was acquainted with these being called "analog RGB" but never saw "analog" > and "CGA" together before.
I susepct it means that it's 3 analogue signals (one for each colour) at the CGA (== US TV, RS170) scan rates. As opposed, say, to VGA which is 3 analogue signals with a rather higher horizontal scan rate. > 2. There are computers knocking about with actual digital RGB signals, like > the BBC Micro B (IIRC). What I forgot to make explicit in my question was Yes, it dodes. The BBC micro has 3 TTL signals on the RGB connector. A total of 8 possible colours. > that I was asking about RGBI (+intensity), which AIUI is the same as CGA. Normally yes. I don't see any reason why RGBI signals could not be used at a different scan rate, but AFAIK no machine ever did. > Now, I'm confused about point 1: did actual PCs with CGA have both digital > (TTL) and analog signaling? Not really. The original CGA card, and most clones, have a composite video output too with NTSC-encoded colour, but that is not what you are asking about. -tony
