Region free MEGA-CD and SEGA-CD BIOSes

Started by l_oliveira, June 30, 2010, 04:08:50 AM

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l_oliveira

June 30, 2010, 04:08:50 AM Last Edit: July 01, 2010, 12:59:43 AM by l_oliveira
Thanks to Russell OQuigley (RAQ) excellent work on reverse engineering the PAL MEGA-CD SUB-CPU BIOS this become possible:

At http://www.assemblergames.com/forums/showthread.php?p=426905#post426905 :
QuoteHere is a link to a modified Europen BIOS i did http://gendev.spritesmind.net/forum/viewtopic.php?t=726  This 'hack' removes the country protection check and the CD security check, it's not perfect but it does work. It's only been tested on an emulator (Kega Fusion) but i don't see why it wouldn't work on actual hardware.

Thanks to RAQ's work on the SUB-CPU bios I was able to put this MEGA/SEGA-CD BIOS package together with slightly extra bit of hacking:

http://www.4shared.com/file/vjQbI31Z/MEGA-CD_FREE_JUE.html


This is a mirror of RAQ's original release:

http://www.4shared.com/file/V899xMfH/_BIOS__Mega-CD__World___v100_.html


The JP one contains his patched SUB-CPU BIOS and extra patches on the MEGA Drive side of the code to aways display the "PRODUCED BY OR UNDER LICENCE OF KABUSHIKI KAISHA SEGA ENTERPRISES" regardless of the inserted disc region. His patch to the PAL ROM  displays the SONIC logo on PAL or NTSC export discs and skips the logo if the disc is Japanese/domestic.

To achieve this I replaced the original SUB-CPU BIOS with RAQ's, changed the MEGA-CD MD side BIOS call at 0x0364 to point to a patched copy of the Japanese logo at 0x6F20 which executes and then returns execution to the game.


Edit:    File failed on real hardware due to wrong SEGA checksum. Has been repaired and archive has been replaced.
Edit2: File has been edited again and now contains patched BIOSes for all TRAY loading based models: US SEGA-CD, PAL MEGA-CD and JPN/Asia (Pal compatible) MEGA-CD.