How many USB and Firewire ports of what type do the Power Mac G4 models have? Can you upgrade the ports to USB 2.0 and Firewire 800?

All Power Macintosh G4 models have a minimum of two external USB 1.1 ports and two external Firewire 400 ports.

The "AGP" models -- the Power Mac G4 350 (AGP), 400 (AGP), 450 (AGP), and 500 (AGP) -- also have one internal Firewire 400 port. The aptly-dubbed "Firewire 800" models -- the Power Mac G4 1.0 (FW 800), 1.25 DP (FW 800), and 1.42 DP (FW 800) -- have a single external Firewire 800 port as well as dual external USB 1.1 and Firewire 400 ports.

You can't "upgrade" the existing ports, but you certainly can install a PCI card with USB 2.0 ports or Firewire 800 ports in any of the Power Mac G4 models.

Site sponsor Operator Headgap Systems sells a PCI card with five USB 2.0 ports compatible with a Power Macintosh G4 booting MacOS X -- it will run in MacOS 9 with OHS provided drivers as well but only at the slower USB 1.1 speed -- for less than US$25 including shipping in the continential US. Site sponsor Other World Computing has a wide variety of USB 2.0, Firewire 400, and Firewire 800 PCI cards from which to choose.

What type of Ethernet is standard in the Power Mac G4 models? What Gigabit Ethernet upgrade options are available?

Starting with the appropriately named "Gigabit Ethernet" models, all Power Macintosh G4 models already have Gigabit Ethernet onboard. The earlier "PCI" and "AGP" models only have 10/100Base-T Ethernet onboard but can support faster Ethernet with the installation of a Gigabit Ethernet PCI card.

Site sponsor Operator Headgap Systems offers a Gigabit Ethernet card that works in both MacOS 9 and MacOS X and is available for less than US$25 including shipping in the domestic US.

What is the "Velocity Engine"? What makes Velocity Engine faster?

The Velocity Engine is a 128-bit vector processing unit that is part of the PowerPC 74xx (G4) processor.

Previously associated with expensive supercomputers, Apple explains that the Velocity Engine has:

162 new dedicated instructions integrated into silicon can be used to greatly accelerate intensive multimedia and math calculations. [The Velocity Engine] does this by working on a whole set of data simultaneously, rather than one data point at a time. The Velocity Engine also operates completely independent of both the integer unit and the floating-point unit, enabling all three units to process data at the same time.

How can you tell if a particular Power Mac G4 model is PCI or AGP-based?

Apple explains that the easiest way to determine if a particular Power Macintosh G4 computer is PCI-based or AGP-based by external inspection is to look at the sound ports on the back of the computer. On Yikes! PCI-based models, the sound ports are horizontally aligned, and on Sawtooth AGP-based models, the sound ports are vertically aligned.

All subsequently released Power Mac G4 models are AGP-based. The "Gigabit Ethernet" models look the same externally as the original AGP models, but the "Digital Audio" models also can be distinguished from earlier AGP-based models by paying attention to port layout. Besides the extra PCI slot, the sound ports have been moved to the top, and the "soft" power plug has been removed.

The "Quicksilver" models can be easily identified by their light silver color (the earlier models are dark gray) and the "Mirrored Drive Doors" line can be spotted by the "mirrored finish" external drive bays and decorative indentions on the front reminiscent of the "Ventiports" on a 1949 Buick Roadmaster.