Splitting connected ROMs (S3&K, from Sega Mega Drive/Genesis Classics)

[TheNametag]

Is there a known way to separate the Sonic 3 and Sonic & Knuckles individual ROMs from the combined ROM found in the Sega Mega Drive & Genesis Classics? For a few reasons. First, to have the original versions available, and second in order to then combine Sonic & Knuckles with the other games to get Knuckles in Sonic 2, and Blue Sphere.

[farmerbb]

The Sonic_Knuckles_wSonic3.bin file is just the Sonic & Knuckles ROM with the Sonic 3 ROM appended to the end of it. On Linux you can split the ROMs by running these commands:

split -b 2M Sonic_Knuckles_wSonic3.bin
mv xaa "Sonic & Knuckles.bin"
mv xab "Sonic the Hedgehog 3.bin"

On Windows you can use 7-Zip to split the file, just browse to the Sonic_Knuckles_wSonic3.bin file inside 7-Zip, right click -> Split file... -> enter "2M" in the "Split to volumes, bytes:" field. The split file ending in 001 is the Sonic & Knuckles ROM, and the one ending in 002 is the Sonic 3 ROM.

[farmerbb]

Also, while you'll be able to recombine Sonic & Knuckles with a Sonic 1 ROM to get Blue Sphere, sadly you won't be able to recombine it with a Sonic 2 ROM to get Knuckles in Sonic 2 as that game requires additional ROM data present on the Sonic & Knuckles cartridge but not present in the ROM found in Sega Genesis Classics on Steam.

[kjetil-f]

When I combine the Sonic & Knuckles (with 3 removed) with Sonic 1 from Steam, I only get the No Way screen.

[RealRelativeEase]

I might be too late by now, but just in case: You have to press all three face buttons at once on the No Way screen.

[TheNametag]

Thanks for the info. I was able to get the ROMs split, and get Blue Sphere. Shame Knuckles in Sonic 2 isn't obtainable that way.

[PW5190]

The standalone Sonic 3 ROM when separated from Sonic & Knuckles is actually the Japanese version, just like with the uncompressed ROM for Phantasy Star IV.

[farmerbb]

For Sonic 3 the only difference between regional variants is the region code in the header. There are no other changes in the ROM

[SlashEraser]

Sonic & Knuckles Lock-On.zip

Drag the S3&K ROM onto s3k_separator.exe, and you will get the Sonic 3 and Sonic & Knuckles ROMs. Rename the extension to .bin.
Then, use Sonic & Knuckles Lock-On ROM Creator V1 or V2 to combine Sonic & Knuckles with Sonic and Sonic 2 to get Blue Sphere and Knuckles in Sonic 2.