in the iMac G4 i was wondering why certain cd/dvd drives work and certain ones don't

if i put one in it wont recognize the cd drive or the hard drive
if i put another in it will recognize only the hard drive
and if i put in the original one in it will recognize both
i heard it had something to with jumpers or something which i don't quite understand either

This is a 17" iMac 800MHz