Re: RGB card

[mdj <mdj.mdj@gmail.com>]

On Nov 14, 6:50 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
> mdj wrote:
> > The 80COL and AN3 softswitches are used in the IIe to enable Double
> > Hires and Lores modes. The Video7 RGB adapters established a protocol
> > for toggling these switches in certain sequences which enable
> > selection between DHR colour, mono, mixed, and '160' modes. There's
> > also a FG/BG mode that lets you do 280x192 single hires, and the AUX
> > page holds the FG/BG colours for each screen byte.
>
> > Using the protocol allows software to 'support' RGB cards by selecting
> > whatever mode is appropriate with completely benign results on non-RGB
> > equipped Apple II's.
>
> Ah, yes--"backward compatibility" for the new software, and simpler
> than providing a scheme for software to detect the card's presence
> (or absence).  Just what I would have done in the circumstance.  ;-)

It's an excellent design. I never did figure out if the IIc versions
could interpolate the switching protocol somehow from the expansion
connector. One of these days I'll have to grab such an adapter and
test it out.

I always thought it a shame that the IIgs didn't support this. It did
provide a way to do colour/mono selection, but it was rare that I
found a mono-dhr application that didn't require me to activate
monochrome in the control panel.

Matt