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Author Topic: Removing Modchip detection from Sakura tetris PSX  (Read 1343 times)

Drag0nscythe

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Removing Modchip detection from Sakura tetris PSX
« on: June 12, 2019, 04:48:52 am »
The tetris Sakura game for the PSX has an anti-PS1-modchip check which prevents some emulators from playing the game. This is particularly a problem for the PS Vita where the 6.10 pops fails to pass the check. Thankfully a code was generated and shared on reddit which can bypass the check using the cwcheat plugin.


https://www.reddit.com/r/PSP/comments/4j3snf/has_anyone_ever_managed_to_make_tetris_with/

Is it possible to take the code and modify the iso to bypass the check automatically?

Mugi

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #1 on: June 12, 2019, 06:00:20 am »
im not really familiar with how CWCheat addresses work, but it should be just a matter of converting those addresses to the addresses
in the iso and applying the changes to it directly.

someone more knowledgeable regarding how CWCheat works shouldn't have much issues dealing with it i believe.
In PSP we trust.

Z3R0X

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #2 on: June 12, 2019, 12:08:14 pm »
The tetris Sakura game for the PSX has an anti-PS1-modchip check which prevents some emulators from playing the game. This is particularly a problem for the PS Vita where the 6.10 pops fails to pass the check. Thankfully a code was generated and shared on reddit which can bypass the check using the cwcheat plugin.


https://www.reddit.com/r/PSP/comments/4j3snf/has_anyone_ever_managed_to_make_tetris_with/

Is it possible to take the code and modify the iso to bypass the check automatically?

That is not hard if you already have the RAM patch code.

Drag0nscythe

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #3 on: June 13, 2019, 02:51:48 am »
From the documentation I can find about cwcheat, the plugin edits the PSP ram locations which in turn edits the game.

found here (https://github.com/hrydgard/ppsspp/issues/3551)


As it affects the RAM, Do I create a patch that runs before the game to patch the RAM upon loading?

Very new to hacking psx games especially in removing DRM.

Z3R0X

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #4 on: June 13, 2019, 04:12:12 am »
From the documentation I can find about cwcheat, the plugin edits the PSP ram locations which in turn edits the game.

found here (https://github.com/hrydgard/ppsspp/issues/3551)


As it affects the RAM, Do I create a patch that runs before the game to patch the RAM upon loading?

Very new to hacking psx games especially in removing DRM.

I can do a patch to remove the check.
I need the full game name, version (if they exist) and region.

Drag0nscythe

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #5 on: June 14, 2019, 10:41:45 am »
Thanks a bunch

The details of the game are as follows. I pulled this from the redump website:

Tetris with Cardcaptor Sakura Eternal Heart
テトリス with カードキャプターさくら エターナルハート

System   Sony PlayStation
Media   CD
Category   Games
Region   Japan
Languages   Japanese
Serial   SLPS-02886
EXE date   2000-06-11
Edition   Original
EDC   Yes
Anti-modchip   Yes
LibCrypt   No
Errors count   0
Number of tracks   1
Write offset   +1

 and If possible, is it possible to explain what you did to make the patch?

Z3R0X

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #6 on: June 15, 2019, 12:36:11 pm »
Here is the patch, that has EDC/ECC correction just for the sake of it :thumbsup:
http://www.mediafire.com/?9njoje999l952bo
Let me know if the game run as intended.
How I did the patch?
I use the CW codes that you post to get the offsets of the DRM instructions and saw a bunch of branch instructions, I just modify the conditional branches for always branches and that it.

Here are the actual offsets that I modify:
RAM means RAM offsets and ROM means the actual BIN offsets both in HEX, the 4th line is the original MIPS instruction and the last line after the <> is the modified MIPS instruction.
Code: [Select]
Check 1
RAM = 0x80016B58
ROM = 0x00016090
06 00 62 14
<>
15 00 00 10

Check 2
RAM = 0x800217C4
ROM = 0x000225EC
05 00 62 14
<>
0F 00 00 10

Check 3
RAM = 0x800201B0
ROM = 0x00020D78
05 00 82 14
<>
0F 00 00 10

Enjoy man! ;D
« Last Edit: June 15, 2019, 12:42:31 pm by Z3R0X »

Drag0nscythe

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Re: Removing Modchip detection from Sakura tetris PSX
« Reply #7 on: June 15, 2019, 11:36:10 pm »
Works fantastically. Thanks a bunch,

And thanks for the explanation as well.  :thumbsup: