Re: Alternate Display Mode?

[nathan@cco.caltech.edu (Nathan Mates)]

In article <h6yeyOv.sjc@delphi.com>, Stephen Carpenter  <sjc@delphi.com> wrote:
>I have a ROM 1 GS and am wondering What does Alt. Display mode do?

   In the Apple II display modes (40/80 col text Text, LoRes Graphics,
Hires (280x192) and Double Hires (560x192) graphics, plus mixed
modes), each possible mode has 2 'pages' that can be displayed. Thus,
a program can display one screen, draw on the other, display that, and
work on the first.

   Anyhow, in the GS emulation of the Apple II modes, almost all modes
are handled normally by the hardware. But, the second text screen (not
really used very much at all) isn't displayed this way. Therefore, the
few programs that tried to use this screen mode wouldn't work, putting
up a screenfull of garbage, usually '2's.

   That's where the Alt Display Mode comes from. It sets up a
background task to copy the page to the memory where it's displayed
from so it looks right. If you must view this display area, it's a
real useful tool. If you're like the 99% of us who never have any
cause to use it, it's an extra entry in the CDA menu, and eats system
time when on.


>I figured that this was probably the place to ask

   Yes, comp.sys.apple2.programmer does have more than its fair share of
tech types. But, the answers apply to all, so I'm redirecting this
thread over to comp.sys.apple2.


>I was having a problem with my modem and in a desparate attempt to solve it
>turned off Alt display mode and that fixed it-

   Probably a high-speed modem. The copying shouldn't muck up a
slower (below 9600) connection.

-- 
<*> Nathan Mates http://www.ugcs.caltech.edu/~nathan/      <*>
# And he said to them, "To you has been given the secret of the
# Kingdom of God, but for those outside, everything comes in 
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