How do you replace or upgrade the hard drive in the Power Mac G4 models? How many hard drives of what type are supported? Which models support "big drives"?

Like upgrading everything else in the Power Mac G4 models, upgrading the hard drive is quick and straightforward. Information regarding the internal hard drive interface and number of drive bays is provided on the specs page for each system, but also is provided in a chart below.

Early Power Macintosh G4 systems use Ultra ATA/33 or Ultra ATA/66 drives and later ones use Ultra ATA/66 and Ultra ATA/100 drives, but since the Ultra ATA standard is backwards compatible -- an Ultra ATA/100 drive also works in an Ultra ATA/33 or Ultra ATA/66 equipped Mac, just at the slower speed -- and it could prove to be challenging to track down a pre-Ultra ATA/100 drive, the shortest answer to the drive type question is essentially "Ultra ATA/100".

On the original bus -- without installing a third-party controller PCI card -- all pre "Mirrored Drive Doors" models can support two drives and the "Mirrored Drive Doors" and "Firewire 800" models can support four. By installing a PCI card, all of the available 3.5" drive bays can be occupied by hard drives and additional types of hard drives -- SCSI or SATA, for example -- can be installed as well.

Officially, Apple says that the Power Macintosh G4 "Mirrored Drive Doors" models as well as "any other model introduced after June 2002" can support "big drives" (128 GB and larger). Although this means that only the "Mirrored Drive Doors" and "Firewire 800" lines formally support 128 GB and larger drives, readers have discovered that the "Quicksilver" and "Quicksilver 2002" models also support 128 GB and larger drives when booting MacOS X 10.2 or higher.

Pre-Quicksilver models -- or pre-Mirrored Drive Doors models booting MacOS 9 -- typically need a third-party driver, such as those from Intech or GenThree to use hard drives larger than 128 GB. A modern third-party controller card also will allow one to get around the limitation, and as first spotted by helpful reader "Michael B. in Cincinnati" in EveryMac.com's own forums, hacks are possible as well. For the Mirrored Drive Doors models, Apple reports that these can recognize a 200 GB partition when booting MacOS 9 if it was formatted with MacOS X 10.2 or later.

Technical details, as well as direct links to PDF installation instructions from Apple -- replacing the original drive -- and video installation instructions from site sponsor Other World Computing -- installing a controller card and another drive -- follow:

PM G4	Int. HD Interface	Drive Bays	Instructions
PCI	Ultra ATA/33*	5 3.5", 1 5.25"	Apple & OWC
AGP	Ultra ATA/66*	5 3.5", 1 5.25"	Apple & OWC
Gigabit	Ultra ATA/66*	5 3.5", 1 5.25"	Apple & OWC
Digital Audio	Ultra ATA/66*	5 3.5", 1 5.25"	Apple & OWC
Quicksilver	Ultra ATA/66*	5 3.5", 1 5.25"	Apple & OWC
QS 2002	Ultra ATA/66*	5 3.5", 1 5.25"	Apple & OWC
MDD	Ultra ATA/100†	4 3.5", 2 5.25"†	Apple & OWC
Firewire 800	Ultra ATA/100†	4 3.5", 2 5.25"†	Apple & OWC
MDD 2003	Ultra ATA/100†	4 3.5", 2 5.25"†	Apple & OWC

* An Ultra ATA/100 drive also works in an Ultra ATA/66 or Ultra ATA/33 equipped Mac, just at a slower speed.

† These models have four internal 3.5" drive bays -- two Ultra ATA/66 and two Ultra ATA/100 -- intended for hard drives and two external 5.25" drive bays intended for optical drives. For complete details regarding drive bays in all models, please refer to the applicable specs page for the model of interest.

This video from Other World Computing is for the "AGP Graphics/Gigabit Ethernet" line and covers installation of a Serial ATA drive and a PCI card:

Additionally, OWC has hard drive upgrade videos for the "Quicksilver/Quicksilver 2002" and "Mirrored Drive Doors/Firewire 800" models.

As well as helpful upgrade videos, as you would expect, OWC has hard drives for sale compatible with every Power Macintosh G4 model. Site sponsor Operator Headgap Systems also has hard drives available.