Apple has posted
SuperDrive Firmware Update v2.0, intended for certain 12, 15 and 17-inch PowerBook G4s, iMac G5s and Mac mini G4 systems (a list of the affected models is available from Apple’s Web site).
According to Apple, the update fixes the burning speed of those systems’ SuperDrive internal optical disk drive when writing to certain recordable DVD media.
The updater will check the system it’s run on to determine its suitability for the update. Apple advises users not to reset, shut down or turn off power to their computers while the update is running, otherwise the SuperDrive could be damaged.