Thanks for feedback Roger. I agree I think this Video board is something we really have to solve to get a decent DOS baseline for future S-100 Boards (80386 etc…) I want to try and do all further development in DOS with these systems. I also feel somehow it has to be 6845 (exact) hardware compatible. I just cannot find a dual ported RAM circuit to get started that does not have PAL’s (as the Lomas and CompuPro boards had) . One possibility would be to use a later CGA “all in one” board on a chip IC. These would probably be surface mount, but there are outfits that will solder them in for you for a fee $ each.
Anything you come up with will be great
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of norwe...@aol.com
Sent: Sunday, July 17, 2011 12:48 PM
Subject: Re: [N8VEM-S100:353] S-100 Vido board with 6845
Interesting! The 800 lb. gorilla in the room that everybody *tries* to ignore seems to be S100 video (80x24 or 25, that is).
Perhaps there is another option besides the 6845? Intel came out with a similar controller about the same time as Motorola introduced the 6845 - the i8275. It has similar capabilities, I think. There was a fellow (in Illinois, I believe) who sold a S-100 card, based on the i8275, back in the mid-80's. The big(?) selling point was that it produced VGA video (at a time when the whole microcumputer world was moving toward IBM and MS-Doze). I think I have one here somewhere, and maybe even a schematic and documentation? Might take me a while to find it, however (*grin*). I have NO idea about the availability of the i8275 anymore. It was a 40-pin DIP.
As far as the 6845 goes, the only video circuit I ever saw was one published in "Byte", in the Ciarcia column? Am I dreaming this? Anybody else confirm? Considering the source, it was most certainly NOT S-100. *shrug* Oh, and maybe there was another that came out in the "CRT Controller Handbook"? Again, probably NOT S-100. I'll have to look.
Love to hear peoples' thoughts about S-100 video.