Like it was mentioned in the first post it unlocks the hidden characters. Just go to the character selection screen before and after applying the cheat and it should be fairly obvious.
I don't post without reason.
I made the change and there's no discernible difference, there's still eight characters in Taisen mode. Perhaps the other two games will be different, but I want to solve the first one before those. Perhaps someone would be so kind as to provide before and after screenshots to show me what I'm supposed to be seeing, because right now I ain't seeing nothing.
FWIW go to 1708A4 and change B0 to 90 which reverses what it normally does (so no cheat gives you cheats while cheats turn it off).
EDIT: never mind about screenshots, I see a guy on YouTube doing the cheat, now I've managed to perform the cheat myself, and I see all the characters. Now just got to figure out why my change didn't do it...