the code for the cic chips is the boot code all n64 roms go through .. the pif rom boots the n64 and validates that it is a valid boot code .. it basicly crc's the first 1000h bytes then check to see if a value on boot (from rom) matches what the crc is .. if not it just dies. So that is why you can not change the first 1000 bytes and useally the hacks change it to the mario boot code (CIC-NUS-60102), so you can boot with the mario chip .. not all data is in the rom file .. but most are .. as n64 emu do not have to make sure that it is real valid image .. then boot code is fairly useless .. it also hides it self to