Author: Anders Eriksson (kryten.dhs.nu)
Date: 02-04-2003 21:22
There's only one "reliable" trick, it's 16 pixels of the left border.
The other tricks to obtain full overscan is to do it in a really nasty way (hail ulm for their crazyness though).
1. To remove the top border you need to do 60/50Hz switch in the right place, usually timed with timer-a.
2. To remove the lower border you need to do another 60/60Hz switch in the right place..
These two can be done "rather friendly". with simple interupts.
Left and right borders however..
You need to sync the machine completely, turn off everything so there is nothing disturbing. then for every scanline you need to do 70/50Hz switch in the exact right clockcycle (left border) and a 60/50Hz switch in the exact clockcycle (right border).
It's also common to do a med/low res switch to fix some bitplane problems.. Of course in the exact right clockcycle on every damn scanline as well.
Unless you want to sync your normal routs into the scanline-code, you loose as many scanlines CPU as your overscan is high..
Needless to say, this kind of code fails miserably on all accelerators and on all higher-level machines (tt, mste/16, falcon).
--
Anders Eriksson
support@atari.org
|
