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relo999 wrote

@Apocalypse:

I'm still updating the list and added Tom and Jerry, every once in a blue moon I check up here.

Someone could indeed go over every game with an everdrive. Realistically however it's a big hassle as they'd need a lots of time, either a region modded system or 2 different region gamegears. And if you want to be thorough you'd need to complete the game and go through options once for each region, and realize there are differences. Language and splash screen changes would be quite obvious, but difficulty or extra content would be much harder to notice.
Emulation might be an option but as far as I'm aware there isn't an option for it in emulators, granted I'm not all to familiar in the world of emulation.

That said I'd love to see someone have enough dedication to Game gear regional differences to do that. It might be interesting to crowdsource such an effort in combination with the speedrun people. Personally I'm already happy that regional differences are already far more well known for the Gamegear, this post now shows up first in google if I search "game gear forum", hahaha. Now I think of it, I'll check on the speedrun forums if they are aware of region coding in some gamegear games.

BTW thanks for the writeup about region modding the gamegear.

BTW Meka allows console region to be set in the menu, including for Game Gear

Could one tell by ROM analysis which games have something region-related? To just check which games are looking at the region bit in code, and then from there do more examination on individual games.

KingMike wrote

Could one tell by ROM analysis which games have something region-related? To just check which games are looking at the region bit in code, and then from there do more examination on individual games.

Of course! However this requires disassembling the ROM / tracing through its code. In some cases pattern-matching on typical region-checking instruction sequences may be enough, but there are actually quite a few different opcode patterns used for that purpose

bsittler wrote

Of course! However this requires disassembling the ROM / tracing through its code. In some cases pattern-matching on typical region-checking instruction sequences may be enough, but there are actually quite a few different opcode patterns used for that purpose

Couldn't this be done the other way around? I assume a game just checks one bit somewhere on the console that checks for region. At least one pin needs to be high or low when physically changing the region of the console.
So with a modified emulator that checks for region you could set a flag for when that region bit is read.

Of course at that point you still don't know what it changes or if that check actually changes anything, but it'd be a good way to rule out games that dont check for region at all.

It’s likely plenty of games check without making use of the result if it’s in some standard library.

For Game Gear the region info (JP vs "overseas") is packed into the same 8-bit I/O port 0x00 as some unrelated bits, namely NTSC vs PAL and the state of the Start button. The third one (reading the Start button state) is by far the most common use for data bytes read from this port, but sometimes both things are checked simultaneously, or rather the byte is stored in RAM and only later read by two different pieces of code - one that cares about the region bit(s), and another that cares about the Start button state

Author	Message
bsittler Joined: 22 Apr 2018 Posts: 530	Posted: Wed Jul 19, 2023 7:32 pm
bsittler Joined: 22 Apr 2018 Posts: 530	relo999 wrote @Apocalypse: I'm still updating the list and added Tom and Jerry, every once in a blue moon I check up here. Someone could indeed go over every game with an everdrive. Realistically however it's a big hassle as they'd need a lots of time, either a region modded system or 2 different region gamegears. And if you want to be thorough you'd need to complete the game and go through options once for each region, and realize there are differences. Language and splash screen changes would be quite obvious, but difficulty or extra content would be much harder to notice. Emulation might be an option but as far as I'm aware there isn't an option for it in emulators, granted I'm not all to familiar in the world of emulation. That said I'd love to see someone have enough dedication to Game gear regional differences to do that. It might be interesting to crowdsource such an effort in combination with the speedrun people. Personally I'm already happy that regional differences are already far more well known for the Gamegear, this post now shows up first in google if I search "game gear forum", hahaha. Now I think of it, I'll check on the speedrun forums if they are aware of region coding in some gamegear games. BTW thanks for the writeup about region modding the gamegear. BTW Meka allows console region to be set in the menu, including for Game Gear

KingMike Joined: 14 Oct 2008 Posts: 513	Posted: Fri Jul 21, 2023 2:23 pm
KingMike Joined: 14 Oct 2008 Posts: 513	Could one tell by ROM analysis which games have something region-related? To just check which games are looking at the region bit in code, and then from there do more examination on individual games.

bsittler Joined: 22 Apr 2018 Posts: 530	Posted: Fri Jul 21, 2023 8:15 pm
bsittler Joined: 22 Apr 2018 Posts: 530	KingMike wrote Could one tell by ROM analysis which games have something region-related? To just check which games are looking at the region bit in code, and then from there do more examination on individual games. Of course! However this requires disassembling the ROM / tracing through its code. In some cases pattern-matching on typical region-checking instruction sequences may be enough, but there are actually quite a few different opcode patterns used for that purpose

relo999 Joined: 30 May 2020 Posts: 10	Posted: Sun Jul 23, 2023 2:09 pm
relo999 Joined: 30 May 2020 Posts: 10	bsittler wrote Of course! However this requires disassembling the ROM / tracing through its code. In some cases pattern-matching on typical region-checking instruction sequences may be enough, but there are actually quite a few different opcode patterns used for that purpose Couldn't this be done the other way around? I assume a game just checks one bit somewhere on the console that checks for region. At least one pin needs to be high or low when physically changing the region of the console. So with a modified emulator that checks for region you could set a flag for when that region bit is read. Of course at that point you still don't know what it changes or if that check actually changes anything, but it'd be a good way to rule out games that dont check for region at all.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	Posted: Sun Jul 23, 2023 2:35 pm
	It’s likely plenty of games check without making use of the result if it’s in some standard library.

bsittler Joined: 22 Apr 2018 Posts: 530	Posted: Sun Jul 23, 2023 4:44 pm
bsittler Joined: 22 Apr 2018 Posts: 530	For Game Gear the region info (JP vs "overseas") is packed into the same 8-bit I/O port 0x00 as some unrelated bits, namely NTSC vs PAL and the state of the Start button. The third one (reading the Start button state) is by far the most common use for data bytes read from this port, but sometimes both things are checked simultaneously, or rather the byte is stored in RAM and only later read by two different pieces of code - one that cares about the region bit(s), and another that cares about the Start button state

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