[hatari-devel] Chaos AD problem : $fffffc02

[Nicolas Pomarède]

Le 13/06/2011 22:32, Eero Tamminen a écrit :
> Hi,
>
> On maanantai 13 kesäkuu 2011, Laurent Sallafranque wrote:
>> Thanks a lot Nicolas.
>>
>> Another demo that runs now ;)
>>
>> For me, it has freezed while showing the tridi DNT crew logo (near the
>> end of the demo I guess).
>
> For me it works to the end (there are still several screens after the
> blue-white tridi DNT logo), when using the old UAE core.

In my case, it was also using the old UAE core (although I get one 
freeze once during the kind of "fractal color cycling" tiled screen)

>
>> I agree, the sound is awfully noisy (one of the most noisy sounds I've
>> heard under hatari).
>
> Credits at the end say it's DSP sound.  :-)

Yes, and there're a lot of dsp traces if your turn them on

>>>
>>> Hopefully, the demo doesn't uses the 6301's code that was supposed to
>>> decode the byte. The 6301 code is using some kinds of 'sync decoding',
>>> by relying on the 6301's timer counter and the instructions cycle
>>> length.
>
> At what frequency that timer is running, are you saying that it could
> be using IKBD for synching the sound?

No, the ikbd is used at the start to "decrypt" the demo (during the 
floppy disk picture) ; it's a kind of protection for preventing other 
people to rip your code.
Once the demo starts, the ikbd is not used anymore (it would be 
impossible to use it for any real time effect, as it takes approx 8000 
68000 cpu cycles to send 1 byte)

I was refering to some "sync code" in the 6301 decoder, because it was 
supposed to use the content of the 6301's free clock run counter to 
decrypt the bytes, which means you can't run the code "by hand" at a 
slower speed, you need to really run it on the ikbd if you want to get 
proper decoding, which makes things harder to debug if you want to crack 
the protection (this is similar to the protections that use the content 
of $ff8209 to decode some part of a program).



Nicolas