Apple has added a new article to the Knowledge Base regarding the use of hard drives over 128GB in size. Appleis Knowledge Base (sometimes referred to as the KBase) is a central location for all of Appleis support documents and other important information.

Hard drives that are larger than 128GB require an IDE controller with 48-bit LBA support. If the IDE controller does not have that support, you will not be able to use more than 128GB. This only applies to hard drives connected to the IDE bus. FireWire and SCSI drives are not affected. Macintoshes that support 48-bit LBA include the Power Mac G4 (Mirrored Drive Doors) and the Xserve. The article also notes that using these drives requires Mac OS X 10.2 or higher. According to Apple:

There are two primary requirements that must be met for higher capacity hard drives to be fully utilized within a computer.

1. The computer must have Mac OS X 10.2 or later.

2. The computer must provide support for the drives via the BootROM.

Mac OS X 10.2 or later

The high capacity drive must be formatted using Mac OS X 10.2 or later for the full capacity of the drive to be available. Once formatted, the drive will be recognized under the version of Mac OS 9.2.2 that comes with the Power Mac G4 (Mirrored Drive Doors) and later products.

If the drive is not formatted using Mac OS X 10.2 or later, the maximum volume size available is limited to approximately 128 GB.

Support via the BootROM

The BootROM of Power Mac G4 (Mirrored Drive Doors) computers and Xserve computers can accommodate these larger drives, although Apple does not provide technical support for user-installed upgrades in Xserve computers via the built-in drive carriers.

Both Power Mac G4 (Mirrored Drive Doors) computers and Xserve computers can take advantage of drives connected via the FireWire interface.

You can find the new Knowledge Base article at Appleis Web site.