Aside from doing it the raw way, I also want to try using a 6845 I
> ordered last year to generate video. I think I've wrapped my head
> around how it works fairly well, but after looking at CGA register
> values, I found myself confused. It seems that if you're going to
> run
> in either 320x200 or 640x200 graphics modes, you don't set the number
> of vertically displayed rows to 200 as one might think, but 100
> instead. I don't understand this, or how the screen would then be
> displayed properly, since it seemingly is only doing half the screen.
> As far as I know, CGA doesn't ever interlace the actual screen,
> despite the graphics memory being laid out interlaced (which I'm sure
> is related to this somehow). If anyone can shed any light on this
> for
> me, I'd sure appreciate it!
Perhaps this pertains to something known as "Double Scan". I recall this from my early Linux days tinkering with XFree86 "ModeLine" statements.