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Is there a way to patch a rom to play in English on a Japanese SMS?
Posted: Sun Jan 28, 2024 4:24 am
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For example, running "Zillion" on a Japanese SMS will result in the game in Japanese, regardless of the rom dump. Same with Penguin Land and a few others.
Is this something completely controlled by the BIOS or is there something that can be patched in the rom itself to force it to be in English? |
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Posted: Sun Jan 28, 2024 8:15 am |
It’s entirely done in the game code, it is normally done as seen here:
https://www.smspower.org/Development/RegionDetection |
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Posted: Sun Jan 28, 2024 7:54 pm |
That's good to know, so it should be possible to patch roms to force the region.
Unfortunately I do not know ASM. Is there hex value that should be changed to force USA region, or a tool that you know of that patches region for SMS roms? |
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Posted: Sun Jan 28, 2024 9:38 pm |
No, it’s not as simple as that. It may be possible one up with a hex sequence that can patch out the check in many cases but maybe not all. | |
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Posted: Mon Jan 29, 2024 4:18 am |
I appreciate the response. I guess like Ringo once said, it don't come easy. |
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Posted: Mon Jan 29, 2024 7:33 am |
out ($3f),a produces hex D3 3F. Overwriting to 00 00 might do the trick. You’d expect to find it only twice, near the start of the ROM; if you find many then patching than all is likely to corrupt the game. | |
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Posted: Mon Jan 29, 2024 4:52 pm |
I appreciate the help but that does not appear to do anything. There are three instances of D3 3F in hex for "Zillion" for example. The changes do not seem to affect anything. |
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Posted: Tue Jan 30, 2024 9:25 am |
try looking for D3 3F DB DD and replace with D3 3F 3E FF the first time and D3 3F 3E 00 the second time... this should fool the detection
explanation: we're replacing out ($3f),a
with
in a,($dd) out ($3f),a
or with
ld a,$ff out ($3f),a
simulating the results an export system would give
ld a,$00 |
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Posted: Tue Jan 30, 2024 4:57 pm |
This absolutely WORKED! Thank you, much appreciated! I have applied the patch to a few games and they work perfectly on a Japanese SMS in English. I really appreciate the help! |
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