Re: Double GR 80x48

[salfter@salfter.dyndns.org (Scott Alfter)]

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In article <ZG2Bb.118081$do1.114396@twister.austin.rr.com>,
Bryan Parkoff <nospam@nospam.com> wrote:
>    I have tried double GR 80x48 since single GR only support 40x48.  In
>fact is that earliest Apple II and later models do not have firmware to
>support double GR 80x48, but you can be able to write routine that will
>support.

The II and II+ don't have the hardware to support this mode.  A IIe will
handle it if an 80-column card is installed (it doesn't have to be the
extended 80-column card, but that is by far the most common).  The IIc,
IIc+, and IIGS have the necessary hardware built-in.

The IIc also has some undocumented support for double Lo-Res in BASIC. 
Nibble wrote it up...I think you switch to 80-column mode, hit AN3 in
whatever way would normally enable double Hi-Res graphics, and then issue
GR.  Instead of the normal Lo-Res graphics, you get double Lo-Res.  All of
the Lo-Res drawing commands (COLOR=, PLOT, HLIN, VLIN, SCRN) are available,
and I think you get the same 16 colors.  This might also be in the IIc+.  I
know it's not supported in the IIe and IIGS...you need to twiddle the
framebuffer manually, just like you would with DHR.

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