Firmware update
From time to time, Apple releases firmware updates for their computers. This trend is most common in computers released since the original bondi blue iMac in summer 1998. All of these computers have USB, and many have FireWire.
Firmware updates often have a beneficial effect on the speed of the computer, the features it supports (such as Target Disk Mode), the ability to sleep in Energy Star mode, among others. Some -- but very few -- firmware updates will introduce problems, such as an infamous update that disabled some memory installed in Power Macintosh G4 towers. In general, a firmware update improves system stability -- and even the infamous update attempted to do that, by disabling RAM that did not meet strict specifications for Power Mac G4 computers.
Typically, the firmware updates will be downloaded by the "Software Update control panel" in classic Mac OS. They may also be available separately as individual downloads from the Apple Software Downloads Web site. In some cases, the firmware updates require an update to the system software before they can be installed. As of this writing, no firmware updates have been made available through Mac OS X Software Update mechanism. In fact, up to this point, you must install all firmware updates from Mac OS 9.
When applying a firmware update, you should follow all on-screen instructions to the letter. Failure to do so could render your computer inoperative and require expensive Hardware repair.
