Obtaining GBA BIOS without a GBA

[Azidus]

I was following a guide on how to extract files from the japanese version of "Pokemon Box" for the gamecube(cloud312.ldblog.jp/archives/50505313.html), although I have the PAL version, I was able to extract the ruby and sapphire roms without much hassle using GC-tool, My real interest however is the GBA bios file on the disc - primarily I want to use it for GBA link between dolphin and VBA-M, in the guide he just copies a block out of the .DOL file using a hex editor, but since we dont have the same version, simply aping his method was fruitless for me.
I have tried searching through the file with "ROMasque" for a 16384 bit long file with a CRC32 of 81977335, but no luck there either.

Has anybody here had any positive experience trying this or something similar? maybe its fair to assume Nintendo has used the GBA BIOS in other projects? does anyone know if there is a GBA BIOS file present when dumping a GBA game from the WiiU VC using DDD?

 

[bennyman123abc]

If I recall correctly, PAL GBAs and NTSC GBAs have different revisions of the BIOS.

 

[Deleted User]

3DS VC releases come with a working GBA BIOS. In fact, that's how I got my copy IIRC, by extracting it from a VC title. Nintendo's 3DS VC emulator actually has the ability to play GBA games (albeit very slowly), and, as such, requires the BIOS.

 

[Azidus]

If I recall correctly, PAL GBAs and NTSC GBAs have different revisions of the BIOS.

Doesn´t surprise me, I expect the one on my disc is the pal one, its possible the CRC32 of 81977335(according to edgeemu) is the US version - I will try to find the correct CRC for the EU version, although it is also possible that nintendo used a slightly edited BIOS in pokemon box, similar to what they did with FDS emulation in animal crossing.

3DS VC releases come with a working GBA BIOS. In fact, that's how I got my copy IIRC, by extracting it from a VC title. Nintendo's 3DS VC emulator actually has the ability to play GBA games (albeit very slowly), and, as such, requires the BIOS.

Cool!, Would you mind telling me how you did that? I sadly dont have the ambassador program on my o3DS with luma, so I dont think I will be able to do it - unless you magically know how to extract the BIOS with only homebrew access ;p, but it will probably be usefull nontheless, it lends credence to the notion that it might be packed in with the WiiU VC GBA releases aswell.

 

[Deleted User]

Cool!, Would you mind telling me how you did that? I sadly dont have the ambassador program on my o3DS with luma, so I dont think I will be able to do it - unless you magically know how to extract the BIOS with only homebrew access ;p, but it will probably be usefull nontheless, it lends credence to the notion that it might be packed in with the WiiU VC GBA releases aswell.

You actually don't need the GBA VC Ambassador games for this, any NES/GB/GBC VC game should work for this. Just grab a .cia of any title that fits this criteria, and extract agb.bin from it.

There are several ways of going about extracting files, however, I recommend using fuse-3ds to mount the title directly and browse its contents. That way, you don't have to deal with the hassle of manually extracting all of a title's contents.

Also, yeah, if I had to guess, the BIOS would probably be packaged with Wii U VC titles as well, if this is anything to go off of.

 

[pasc]

Not sure if this is helpful, but I'll just leave this here... on the floor... so pick it up if you wish:

https://github.com/Nebuleon/ReGBA/tree/master/bios/source
http://mgba.io/2017/06/30/cracking-gba-bios/

 

[bennyman123abc]

@Azidus The BIOS from the download provided should work in Dolphin.
https://gbatemp.net/download/normatts-open-source-gba-bios-compiled.35225/

 

[Azidus]

Sorry for the late reply, I haven´t had access to my 3DS until now.
It was surprisingly easy to get the agb.bin file as you suggested @B_E_P_I_S_M_A_N, I have som experience extracting 3DS VC ROMs using asia81´s "HackingToolKit3DS", so, after exporting the .cia with gm9 and unpacking it with the tool the agb.bin file is located in plain sight inside the "ExtractedRomFS" folder, I have glanced over that file numerous times I just didn´t know what it was for . Also as suggested, I used an extracted GBC game (Wario Land 2) to obtain the bios.
I just needed to rename it to gba.bin, it has the same size and CRC32 checksum as the "official" dump, so it works with the dolphin/VBA-M link no problem!
@pasc & @bennyman123abc Its super cool and convinient that Normmatt has made an open-source BIOS, but I wasn´t able to get the GBA-link between dolphin and VBA-M working using the same procedure as with the official BIOS.

Anyways, thank you guys for the help and suggestions, I hope this will help somebody else in the future.