Re: [hatari-devel] Unbeatable STF demo works only with STE emulation

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 04/02/2015 22:11, Eero Tamminen a écrit :
> Hi,
>
> One more SillyVenture demo has the same problem as Yanartas;
> it's for ST, but works on Hatari only with STE emulation:
> 	http://www.pouet.net/prod.php?which=64511
> 	http://demozoo.org/productions/128052/
>
> Interestingly, this demo is for the monochrome monitor.

Hi

that's a bug in the demo. As some comments pointed on pouet.net, the 
demo only works with tos 1.06, which means STE mode.

The problem is that they test the monochrome resolution at start with a 
wrong code :

$00012904 : 1039 00ff 8260                     move.b    $ff8260,d0
$0001290a : 0c00 0002                          cmpi.b    #2,d0
$0001290e : 6706                               beq.s     $12916
$00012910 : 4ef9 0002 7bd2                     jmp       $27bd2

Only bits 0 and 1 are useful, but on STF unused bits 2-7 are sets to 1 
(or random bits). While on the STE unused bits 2-7 are always set to 0.

So, "cmpi.b #2,d0" can only work on STE ; they should mask unused bits 
before to make it work on STF "and.b #3,d0".

No bug here, this demo was either tested on an non-accurate emulator or 
only on a STE :)


Nicolas