if you have no mod chip, it doesn't have a 512k BIOS to reference. the BIOS is 256k. It looks like it is a soft mod as the 256k bios is the default for a 1.6
Ndure uses PBE if i recall correctly. The point is that you won't have to worry about changing PBE. It's good the way that it is and probably shouldn't be tampered with.