Re: Double low/hi Res

[David.Empson@bbs.actrix.gen.nz]

In article <1992Nov9.235907.3531@mnemosyne.cs.du.edu> sledbett@nyx.cs.du.edu (Shawn Ledbetter) writes:
> I've read somewhere about the Apple ][e/][c/][gs that it can handle
> double lo-res/hi-res.  Does anyone know the poke values or any other
> information I need.  Thanks in advance.

Double Lo-Res is not documented anywhere as an official graphics mode.
Despite this, Applesoft Basic has support for it!  I'm not sure about
the original IIe, but it definitely works on the enhanced IIe, IIc and IIgs.

To enable Double Lo-Res mode:

1. Get into 80-column mode using PR#3.
2. Turn on Annunciator 3 by doing a POKE 49246,0.
3. Use Lo-Res graphics commands as normal, starting with GR.

To restore normal Lo-Res graphics, POKE 49247,0 then do a GR again.

[I'm not sure about the ordering of these pokes - they might be around
the other way.  The manual isn't nearby.]

Note that you have to be in 80-column mode to use Double Lo-Res (or
Double Hi-Res).


Double Hi-Res is enabled in the same manner - 80 column mode, poke the
annunciator, and enable Hi-Res graphics using HGR or whatever.  The
big catch: Applesoft has no support for Double Hi-Res mode, so
you'll get alternating vertical stripes of random data and black
stripes, and drawing will only affect the 'black' areas.

Double Lo-Res requires an 80-column card; Double Hi-Res requires an
extended 80-column card (i.e. 128k RAM).
-- 
David Empson

Internet: David.Empson@bbs.actrix.gen.nz    EMPSON_D@kosmos.wcc.govt.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand