Graphics Hacks, Part II

[mab22@po.CWRU.Edu (Michael A. Balfour)]

OK, after thinking about it a bit, I would tend to agree that the only
interesting thing anybody might want to do with the graphics ROM would
be to invert the colors.  However, after doing some more experimenting,
I'm led to a whole new graphics question.

How the heck does hi-res graphics work???

I realize I should probably just ask this question directly to David, as
most of my questions to date have only been fielded by him, but I
suppose there's always the chance that other people will be interested
in the answer.

Here's what I understand so far:

Each byte of hi-res memory controls seven pixels on the screen.  The top
bit of the byte is used as a delay, which can cause the seven pixels to
be delayed by a half-pixel.  Sort of.  Let me explain what Imk seeing on
my IIc, and maybe somebody can explain how it happens?

Case 1:  poke a 127 into memory, with a 255 underneath it.  You see the
following, where each X represents a half-pixel.
XXXXXXXXXXXXXX
 XXXXXXXXXXXXX