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Sega CD/Mega CD Region Patching Is it possible?

#1 User is offline The Game Collector 

Posted 24 July 2018 - 01:05 PM

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I was looking at some questions from members in a Sega group on Facebook about Sega CD and being able to play games from other regions on your system. I was told while burns from your region will work, burns or real discs from other regions will not. Come to think of I had never tried any Japanese Sega CD ISOs yet, not even in an emulator (which of course would run games from any region regardless.) For those who prefer playing on real hardware I was wondering if it is possible to hack the ISO of a Japanese-only Mega CD release to change the region to USA so you could then burn a copy of it to disc and play it on a US system. Has anyone here tried this before? I imagine all you would have to do is edit some hex values in the header to match those in a US release.

#2 User is offline Overlord 

Posted 24 July 2018 - 01:19 PM

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My understanding is yes, it'd work - you'd have more issues with PAL releases due to the differing frame rate.

#3 User is offline Ralakimus 

Posted 24 July 2018 - 01:57 PM

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There's more than editing the header to convert a game to a different region.

At the start of the IP sector(s) lies the code for the "licensed under SEGA Enterprises" screen as a security measure. However, there are actually different versions of it for each region. When a CD image is built, it includes whichever code is suitable for the region.

So, you'll also need to patch this bit of code as well. US to EU or JP really shouldn't be much trouble, but the other way around will be. The US code is quite a bit larger than the EU and JP code.

Really, one way you can circumvent the region shit is to load the appropriate BIOS from a flashcart or something. Though, as Overlord said, you should be aware of potential issues when running a PAL game on NTSC or vice versa.

Also, you can't just modify the EU or JP code to handle all regions, because the BIOS does check for modifications and if it finds that the code was modified, it won't run the game. (Unless, you also want to modify a BIOS to skip this check)
This post has been edited by Ralakimus: 24 July 2018 - 02:00 PM

#4 User is offline The Game Collector 

Posted 24 July 2018 - 02:51 PM

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I wonder if the original Everdrive MD can load Sega CD Bios or not. I haven't tried that route yet.

#5 User is offline Ralakimus 

Posted 24 July 2018 - 03:17 PM

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I believe it can as long as the Sega CD is attached.
This post has been edited by Ralakimus: 24 July 2018 - 03:18 PM

#6 User is offline SoullessSentinel 

Posted 27 July 2018 - 07:36 AM

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Speaking from experience: Make sure to use a region-modded console (50hz/60hz selectable at least) or you're gonna have a bad time. Things like audio desync (or even crashes) in games using streaming video, as well as the usual 50hz/60hz differences.

I once toyed with the idea of a boot-disc that you could load, and then swap out with a disc of any region, bypassing the BIOS checks, however, the issues caused by 50hz/60hz differences lead me to drop that idea: Especially since you need to modify your console anyway to address that.

The everdrive (or even replacing the Mega CD bios ROM) is a better solution.

This post has been edited by SoullessSentinel: 27 July 2018 - 07:39 AM

#7 User is offline ICEknight 

Posted 27 July 2018 - 11:20 PM

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There's a cartridge called "CD+Plus" which does just that, and which I already dumped and released a while ago but I don't think has been emulated anywhere yet...

Most/all games should work fine between NTSC regions. PAL games might run into some predictable problems such as cutscenes with synchronized sound+video not being so in sync anymore or some FMV adapted to PAL speed just not working.
This post has been edited by ICEknight: 27 July 2018 - 11:23 PM

#8 User is offline mentski 

Posted 29 July 2018 - 05:48 PM

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View PostThe Game Collector, on 24 July 2018 - 02:51 PM, said:

I wonder if the original Everdrive MD can load Sega CD Bios or not. I haven't tried that route yet.


Yes it can, and there are hacked multiregion bioses for the device of your choice, which can also be burnt to an eprom and used as an internal replacement.

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