Re: [hatari-devel] POV 136 & STE emulation?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

On 16/02/2012 22:45, Eero Tamminen wrote:
> Hi,
>
> POV 136 demo disk doesn't work properly with Hatari STE emulation.
> It complains that there's STE HW missing required for the demos?
>
>
> 	- Eero


The STE detection code is not very good :

$00d3a6 : 4bf8 8205                            lea       $ffff8205.w,a5
$00d3aa : 1e15                                 move.b    (a5),d7
$00d3ac : 1abc 004d                            move.b    #$4d,(a5)
$00d3b0 : be15                                 cmp.b     (a5),d7
$00d3b2 : 6700 000c                            beq       $d3c0
$00d3b6 : 1a87                                 move.b    d7,(a5)
$00d3b8 : 33fc ffff 0003 f808                  move.w    #$ffff,$3f808

Unfortunately, Hatari doesn't support modifying $ff8205 and reading it 
back while display is enabled (while the shifter shows some pixels).

As this routine doesn't sync with VBL, it writes/reads at random time 
during the VBL, so there's a 10% chance or so that you might be able to 
be detected as an STE

Maybe moving the mouse or pressing the keys can alter the timings while 
tos is starting the program to get a chance the read happens at the 
right time.

Certainly not the best way to detect an STE ; trying to access dma sound 
is often more precise at it doesn't involve video timings, even on a 
real STE.

Nicolas