The Gossamer logic board has three full-length (12 ") PCI slots, making it capable of taking any PCI cards that have Macintosh drivers available for them (for example, some RealTek-based network adapters, a lot of USB, ATA/IDE and FireWire cards). The most common PCI card upgrades normally added to Beige G3 Power Macs are FireWire cards, USB cards and FireWire/USB combo cards (especially after the release of the first generation iMac, which caused many vendors to start releasing USB peripherals for the Macintosh), 100BASE-TX or 1000BASE-T (gigabit Ethernet) network adapter (for those who need faster than the onboard 10BASE-T), video cards (ATI Radeon 7000 and 9200 cards are a popular choice), ATA/EIDE, Serial ATA and Ultra SCSI cards. Television tuner and radio cards are also often chosen to supplement the AV features on a Wings personality card, or to provide A/V input for models with the Whisper personality card.
Some users have upgraded the Whisper personality card in their Beige G3s with a "Wings" Personality card (which is plugged into the same PERCH slot), and some have upgraded the ROM on their Beige G3s to a newer version (Revision A boards to Revision B or Revision C boards).
For storage, the G3 is capable of taking any ATAPI/IDE hard disks, provided that the drive's size is within the 28-bit LBA limit. This means a G3 is capable of supporting ATA hard disks of up to 137 GB (228 blocks of 512 bytes each). This limitation can be overcome by using an IDE or SATA PCI-compatible card (e.g. Acard or Sonnet) to allow the G3 to use a maximum of 2 drives over the 137 GB limit.
The ATAPI/IDE CD-ROM drive can also be replaced with a CD-RW, DVD-ROM or DVD-RW drive, although care must be taken while purchasing the upgrade as the Mac is incompatible with some drives and may refuse to boot at all if an incompatible drive is installed. Also, many third-party optical drives cannot be used as boot devices with the G3, though they work correctly for normal use, and burning on many third party CD-RW and DVD-RW drives requires either commercial drivers or is unsupported even though reading and booting from the drive may still work. It is also capable of taking SCSI storage devices, and with the presence of the right PCI cards, SATA, USB and FireWire storage devices.
The presence of an onboard SCSI controller (the SCSI controller is codenamed MESH — Macintosh Enhanced SCSI Hardware) and connectors permits the use of Mac-enabled SCSI scanners and storage devices, though this runs at only 5 MB/s.
The G3 can support up to 768 MiB of SDRAM in any configuration (although incompatibility has been reported with some DIMM modules in certain configurations- for example, newer single-sided PC‑133 RAM modules will not be detected correctly if they will be detected at all and if the machine can boot with them in place, and the desktop and all-in-one units required the use of low-profile RAM due to space constraints). It should be able to take 168-pin SDRAM of any speed, though it will run at PC66 speeds. The onboard video RAM can be upgraded from 2 MiB to 6 MiB with a 4 MiB SGRAM module (which runs at 83 MHz on Rev. A machines, and 100 MHz on Rev. B and C machines).
The G3 processor module (a PowerPC 750 plus L2 cache) can be easily changed to the faster model, i.e. 333 MHz and even 366 MHz or 375 MHz with an 83.3 MHz bus (uncommon). Consult a Clocking the Power Mac G3 article for more info.
The CPU can be upgraded as high as a 1.0 GHz G4 or 1.1 GHz G3 using ZIF upgrades from third party vendors, although the user would not see much practical difference in performance on chips faster than 733 MHz due to the system bus limitations, which runs at 66.83 MHz unless overclocked. However, G4 chips running over 533 MHz do not allow the system bus to run faster than 66 MHz, so you cannot overclock the bus if you wish to use one of these G4s. (G3s do allow it.)
The All-In-One can be modified to use a PCI video card with the internal monitor.
The G3 officially supports up to Mac OS X 10.2.8, although some devices will not work under Mac OS X, such as the floppy drive, the video features of the "Wings" personality card, and the 3D graphics acceleration functions of the onboard ATI Rage series video. Support for newer versions is possible with the use of third party software solutions such as XPostFacto, albeit with a few tradeoffs and catches—the biggest being the lack of support by Apple and the fact that a supported PCI video card must be present as support for the onboard ATI Rage series video was dropped completely as of Mac OS X 10.3 (although the most recent versions of XPostFacto also ships with kernel modules that supports the onboard ATI Rage series video, the module is known to still have a few minor bugs). Mac OS X 10.5 Leopard can be run only if a G4 processor upgrade is installed.
Read more about this topic: Power Macintosh G3