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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?

It’s entirely done in the game code, it is normally done as seen here:

https://www.smspower.org/Development/RegionDetection

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?

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.

Maxim wrote

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.

I appreciate the response. I guess like Ringo once said, it don't come easy.

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.

Maxim wrote

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.

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.

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 ($3f),a
in a,($dd)

with

out ($3f),a
ld a,$ff

or with

out ($3f),a
ld a,$00

simulating the results an export system would give

sverx wrote

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 ($3f),a
in a,($dd)
with

out ($3f),a
ld a,$ff
or with

out ($3f),a
ld a,$00
simulating the results an export system would give

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!

Author	Message
eightbit Joined: 12 Aug 2019 Posts: 11	Is there a way to patch a rom to play in English on a Japanese SMS? Posted: Sun Jan 28, 2024 4:24 am
eightbit Joined: 12 Aug 2019 Posts: 11	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?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	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

eightbit Joined: 12 Aug 2019 Posts: 11	Posted: Sun Jan 28, 2024 7:54 pm
eightbit Joined: 12 Aug 2019 Posts: 11	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?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	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.

eightbit Joined: 12 Aug 2019 Posts: 11	Posted: Mon Jan 29, 2024 4:18 am
eightbit Joined: 12 Aug 2019 Posts: 11	Maxim wrote 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. I appreciate the response. I guess like Ringo once said, it don't come easy.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	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.

eightbit Joined: 12 Aug 2019 Posts: 11	Posted: Mon Jan 29, 2024 4:52 pm
eightbit Joined: 12 Aug 2019 Posts: 11	Maxim wrote 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. 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.

sverx Joined: 05 Sep 2013 Posts: 3828 Location: Stockholm, Sweden	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 ($3f),a in a,($dd) with out ($3f),a ld a,$ff or with out ($3f),a ld a,$00 simulating the results an export system would give

eightbit Joined: 12 Aug 2019 Posts: 11	Posted: Tue Jan 30, 2024 4:57 pm
eightbit Joined: 12 Aug 2019 Posts: 11	sverx wrote 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 ($3f),a in a,($dd) with out ($3f),a ld a,$ff or with out ($3f),a ld a,$00 simulating the results an export system would give 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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