[hatari-devel] BITS demo : thread from atari forum

Thomas Huth huth at users.berlios.de
Sun Jul 10 20:17:11 CEST 2011


Am Sun, 10 Jul 2011 20:03:04 +0200 (CEST)
schrieb Anders Eriksson <ae at dhs.nu>:

> On Sun, 10 Jul 2011, Nicolas Pomarède wrote:
> 
> > move.b $ffff8260,d0
> > beq low_res_ok
> >
> > instead of :
> >
> > move.b $ffff8260,d0
> > and.b #3,d0
> > beq low_res_ok
> >
> > nothing we can do about this, his method is wrong and won't work on
> > a real ST.
> 
> Hi,
> 
> it works on my STe. We ran it on that during the Sommarhack
> competition, no problem.

IIRC there are also programs that rely on the upper bits to be 1
instead... e.g. according to the Hatari changelog:

changeset:   1501:422d0df3257d
date:        Fri Dec 26 18:45:10 2008 +0100
files:       src/video.c
description: On ST/STE, set unused bits to 1 when reading $ff8260
	     (fix Awesome Menu 16)

So I wonder whether there is some kind of rule when these bits can be
read as 0 or as 1 ...

 Thomas



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