Super Street Fighter 2 Turbo Difficulty Mod

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   Hi there,
I have a European version of Super Street Fighter 2 Turbo. I love the game, but it's really hard. I read that the Japanese version is much easier, so I thought I'd try modifying my CPS2 board to play like the Japan version.

My SSF2T board is not a phoenix board, and I recently changed the suicide battery. There are plenty of unencrypted ROMs out there, but I wasn't interested in killing my board. Instead I decided to see if I could re-encrypt the Japanese ROMs to work on my board.

The first step was to learn a little about the encryption system from CPS2 Shock, and the Mame Source. The CPS2 uses a Feistel network algorithm to decrypt the ROM code. A little reading about this on Wikipedia showed me that this algorithm is pretty easy to reverse. Only the opcodes are encrypted, so I found an already decrypted ROM image to build a mask which would allow me to re-encrypt only the op-codes. I then modified the MAME CPS2 source code to allow me to decrypt and re-encrypt the Japanese ROM to work on my European B-board. 

Once I did this, I ripped the ROMs from my B-Board and compared them against my hacked version. To my surprise, very little was different. It seems that the ROM image for each terratory is almost the same, with very minor change for the region setting. I found that address 0x460 on sf.03c controls the region setting. Playing around with MAME, I discovered the following settings:

0x460: 0000=japan, 0200=USA , 0400=EUROPE, 0800=ASIA

Digging around that area, I found some other settings too:

0x462: 0000=AM, 0001=OP

I don't know what this does, but the region/title screen changes from AM to OP if the value is non-zero. Does anyone know? I'm very curious!

0x466: 0000=Normal, 0001=SHOW VERSION

This enables Free Play, even in the Japanese version. SHOW VERSION appears on the region/title screen.

0x468: 0000=Normal, 0001=STOP VERSION

Some other websites I found say that STOP VERSION causes the game to enter a debugger if it crashes. I haven't managed to cause a crash, so I can't test it - but it also appears on the region/title screen.

I burned my modified ROM to an EPROM I ordered from China, and it works well so far. The game is far easier in the Japanese version!

I couldn't find this information (specific to Super Street Fighter 2 Turbo) anywhere else using google, so I thought it might come in handy to someone here. It was fun to play around with the ROM data!

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Pantman Members Profile Send Private Message Find Members Posts Add to Buddy List Level Up Joined: 08 January 2015 Location: Wiltshire, U.K. Status: Offline Points: 112	Post Options Post Reply Quote Pantman Report Post Thanks(0) Quote Reply Topic: Super Street Fighter 2 Turbo Difficulty Mod Posted: 24 March 2015 at 11:21pm
	Hi there, I have a European version of Super Street Fighter 2 Turbo. I love the game, but it's really hard. I read that the Japanese version is much easier, so I thought I'd try modifying my CPS2 board to play like the Japan version. My SSF2T board is not a phoenix board, and I recently changed the suicide battery. There are plenty of unencrypted ROMs out there, but I wasn't interested in killing my board. Instead I decided to see if I could re-encrypt the Japanese ROMs to work on my board. The first step was to learn a little about the encryption system from CPS2 Shock, and the Mame Source. The CPS2 uses a Feistel network algorithm to decrypt the ROM code. A little reading about this on Wikipedia showed me that this algorithm is pretty easy to reverse. Only the opcodes are encrypted, so I found an already decrypted ROM image to build a mask which would allow me to re-encrypt only the op-codes. I then modified the MAME CPS2 source code to allow me to decrypt and re-encrypt the Japanese ROM to work on my European B-board. Once I did this, I ripped the ROMs from my B-Board and compared them against my hacked version. To my surprise, very little was different. It seems that the ROM image for each terratory is almost the same, with very minor change for the region setting. I found that address 0x460 on sf.03c controls the region setting. Playing around with MAME, I discovered the following settings: 0x460: 0000=japan, 0200=USA , 0400=EUROPE, 0800=ASIA Digging around that area, I found some other settings too: 0x462: 0000=AM, 0001=OP I don't know what this does, but the region/title screen changes from AM to OP if the value is non-zero. Does anyone know? I'm very curious! 0x466: 0000=Normal, 0001=SHOW VERSION This enables Free Play, even in the Japanese version. SHOW VERSION appears on the region/title screen. 0x468: 0000=Normal, 0001=STOP VERSION Some other websites I found say that STOP VERSION causes the game to enter a debugger if it crashes. I haven't managed to cause a crash, so I can't test it - but it also appears on the region/title screen. I burned my modified ROM to an EPROM I ordered from China, and it works well so far. The game is far easier in the Japanese version! I couldn't find this information (specific to Super Street Fighter 2 Turbo) anywhere else using google, so I thought it might come in handy to someone here. It was fun to play around with the ROM data!

cosine Members Profile Send Private Message Find Members Posts Add to Buddy List Kill Screen Joined: 23 July 2007 Location: Dunfermline Status: Offline Points: 3468	Post Options Post Reply Quote cosine Report Post Thanks(0) Quote Reply Posted: 24 March 2015 at 11:32pm
	Interesting stuff the biggest pain in the arse with the Japanese version was the lack of free play option, when we were using it at shows.
	Of all the things I've lost, I miss my sanity the most.

BigBadWolf Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Forum Patrol Joined: 23 March 2006 Location: Stirlingshire Status: Offline Points: 7562	Post Options Post Reply Quote BigBadWolf Report Post Thanks(0) Quote Reply Posted: 25 March 2015 at 9:48am
	To my knowledge the problem with us/euro ST is the difficulty setting does not work, it's stuck on seven stars of difficulty. Doesn't matter if you turn it down to one star (very easy) it makes no difference to the game, it's still rock hard like it is on seven stars. Fix that, you'll have your game. Personally, I can't get past even the first three fights on the euro game, but I can beat the jap game.
	JAMMA+ ***Sorry.. I have no fcuks left to give!

Pantman Members Profile Send Private Message Find Members Posts Add to Buddy List Level Up Joined: 08 January 2015 Location: Wiltshire, U.K. Status: Offline Points: 112	Post Options Post Reply Quote Pantman Report Post Thanks(0) Quote Reply Posted: 25 March 2015 at 5:37pm
	The difficulty problem is what I was trying to solve. The free play mode is a nice bonus :-)

Davey D Members Profile Send Private Message Find Members Posts Add to Buddy List High Score Joined: 03 July 2014 Location: Grimsby, UK Status: Offline Points: 575	Post Options Post Reply Quote Davey D Report Post Thanks(0) Quote Reply Posted: 25 March 2015 at 6:05pm
	Nice mod :-D I enjoy reading how people figure out how to hack and modify roms. Does the title screen still say ssf2t like it does originally, or does it say ssf2 x grand master Like the jap version?

Pantman Members Profile Send Private Message Find Members Posts Add to Buddy List Level Up Joined: 08 January 2015 Location: Wiltshire, U.K. Status: Offline Points: 112	Post Options Post Reply Quote Pantman Report Post Thanks(0) Quote Reply Posted: 25 March 2015 at 6:12pm
	It becomes identical to the Japanese version, so Japan license screen, title screen (SSF2X) etc. even the character names are changed, and the cut-scene text is in Japanese.

Pantman Members Profile Send Private Message Find Members Posts Add to Buddy List Level Up Joined: 08 January 2015 Location: Wiltshire, U.K. Status: Offline Points: 112	Post Options Post Reply Quote Pantman Report Post Thanks(0) Quote Reply Posted: 26 March 2015 at 7:36pm
	After a little digging online, it sounds like the OP/AM mode just indicates if the board is a rental or purchased board.

WhiteComet Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Kill Screen Joined: 11 May 2009 Location: Gloucester, SW Status: Offline Points: 1065	Post Options Post Reply Quote WhiteComet Report Post Thanks(0) Quote Reply Posted: 05 April 2015 at 10:23pm
	could you just not get better at playing ST?

Pantman Members Profile Send Private Message Find Members Posts Add to Buddy List Level Up Joined: 08 January 2015 Location: Wiltshire, U.K. Status: Offline Points: 112	Post Options Post Reply Quote Pantman Report Post Thanks(0) Quote Reply Posted: 05 April 2015 at 10:30pm
	Where's the fun in that?