Re: Half-Res Graphics?

[see_sig_for_valid_email@no.spam (Simon Williams)]

Dr. Van Thorp <rbowman@ypsitoys.com> wrote:

> This was something that I heard about back around 1985. There was a
> rumored extra graphics mode on the Apple II that was halfway between
> High-Res and Low-Res. Supposedly it had more colors than high res, but
> (naturally) lower resolution. This graphics mode was said to have been
> used in some Apple II games, but no one I knew had any of these games
> to prove the existance of this elusive graphics mode.

To quote someone who knows:

> 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