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Sonic Remastered v2 incompatible #405

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?
1. To start rom and freeze in the black screen
2. Need disable SRAM to play, but I can't
3. This good game hack, it has nekomix themes

What version of the emulator are you using (official, SVN revision,...)?
Genesis plus gx 1.6.0 and 1.7.4, this game is funcional in pc with gens and 
kega (disabled SRAM)

Sonic Remastered v2 rom is availabe in sonic retro

Original issue reported on code.google.com by Kero.Gen...@gmail.com on 6 Jan 2015 at 8:25

Attachments:

GoogleCodeExporter commented 9 years ago 
Why would a hack need SRAM to be disabled ?

Original comment by ekeeke31@gmail.com on 7 Jan 2015 at 7:32

GoogleCodeExporter commented 9 years ago 
do not know, but if not deactivated sram not work this game, other games should 
not disable sram for proper operation of saved game, a strange case sonic 
remastered 2 by default does not save the game, but select levels with code of 
sonic 1 (up, down, left, right, A + start on the menu)

In kega-gens also freezes at startup if it is not removed sram, would be very 
grateful that sram disabled-enabled option will be added in the next review of 
genesis plus gx :), some other game hack also require the option

Original comment by Kero.Gen...@gmail.com on 9 Jan 2015 at 10:20

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GoogleCodeExporter commented 9 years ago 
Out of curiosity, which game hacks also need SRAM to be disabled ? I would 
prefer handling this automatically like with other special games than adding 
another optionnal setting for this.

Also, according to the changelog on Sonic Retro, version 2.0 of this hack added 
a saving feature. How does this work in Fusion with SRAM disabled ? Version 1.0 
works fine right ? Seems odd that you have to disable SRAM in emulators after 
the hack added SRAM support, looks like a bug in the hack rather than a bug in 
emulators  :-/

Original comment by ekeeke31@gmail.com on 9 Jan 2015 at 12:41

GoogleCodeExporter commented 9 years ago 
I ended up looking into it and it's indeed a bug in the hack code regarding 
SRAM support. To sum it up, technically (just in case the author of the hack 
read this someday or someone wants to fix it) the code wants to initialize some 
SRAM value to zero if it is read > 2 but actually does the opposite. Emulators 
which have unitialized SRAM set to 0xFF by default (like Fusion or Genesis Plus 
GX) will cause the game to jump to some undefined code and go in an infinite 
loop)

You can bypass it by simply having a srm file all filled with 0x00 when you 
start the game for the first time, no need to disable SRAM (which only works by 
chance in Fusion). So, simply copy the .srm file above in your /saves/md/ 
directory after renaming it like the ROM file is named if needed. I tested it 
worked fine.

You could also patch the hack bug to get proper SRAM saving in game (it seems 
to save SRAM to some extent with the method above but I suspect this is not 
fully working).

Here is the action replay code to enter to get it fixed:

1D7D04:6E08

You can also enter this in Kega and see that it now works even with SRAM 
enabled.

Original comment by ekeeke31@gmail.com on 10 Jan 2015 at 7:54

Attachments:

GoogleCodeExporter commented 9 years ago 
Author of the hack here. Unfortunately, the hack's been abandoned around 7 
years ago, and I lost its source code in a hard drive crash about 2 years ago.

It's actually kinda weird that it'd screw up in Fusion like that though, 
considering Fusion's what I tested the thing on in the first place (never did 
like Gens).

Original comment by pedro.sa...@ist.utl.pt on 2 Feb 2015 at 12:06