Re: Hopefully last dumb newbie question.

[dempson@actrix.gen.nz (David Empson)]

LJSILICON <ljsilicon@aol.com> wrote:

> Actually, some programmer also used the same area for the second screen of
> Lo-Res graphics, most notably Apple's Shell Games introduction.

OK, so in that case you would get a lo-res screen full of alternating
horizontal stripes (whatever colours 11 and 2 are).

> For this to display properly you must select the alternate display mode.
> 
> I do question the comment about the original GS boards not supporting the
> alternate display mode. I though my Woz supported it before the upgrade
> was performed. It's been so long ago that I could be mistaken.

You misread my article.  I said that the original motherboard doesn't
provide hardware shadowing of text page 2.  Both ROM 00 and ROM 01 have
the Alternate Display Mode CDA which turns on the software copying
mechanism I described.

The 1MB motherboard (ROM 3) has hardware shadowing, which means that
there is no speed penalty when you turn on Alternate Display Mode
(except that writes to text page 2 will now be forced to run at "slow"
speed).

Hm - I wonder if the ZIP and TransWarp know about this?

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand