PCI G4

The PowerMac G4 (PCI Graphics) was announced in September 1999, along with the PowerMac G4 (AGP Graphics). Based on the same motherboard as the "Blue and White" G3, the G4 PCI added a Motorola MPC 7400 processor to an already succesful machine. Apple billed the 7400 as a "Super Computer on a chip", due to the fact that it was capable of excecuting more than a billion instructions per second (a gigaflop). Much of the 7400's speed increase was due to a new set of instructions, which were executed by a new unit on the chip. Motorola refers to this new unit as the "AltiVec" unit, while Apple publicly refers to it as the "Velocity Engine." The Velocity Engine vastly increased the speed of many common processor-intensive tasks.

Originally, the MPC 7400 chip had been planned to debut in the G4 AGP model, but Apple was not able to get the new machine ready in time. The G4 PCI had been in the works in case of such an event, and allowed Apple to ship 7400-equipt machines while they worked out the final bugs of the G4 AGP. The G4 PCI introduced the new case design, similar to that of the B&W G3, but tinted in the new professional color, "graphite." The G4 PCI was priced at a modest £1200, and shipped standard with 64 MB of RAM, a 10 GB hard drive, a 32x CD-ROM, 56 kbps modem. Zip and DVD-ROM/RAM drives were available as BTO options.

There were extreme supply issues with the G4 initially, due largely to Motorola's inability to deliver the 7400 chips in adequate supply. This was further compounded by an "errata" in the initial revision of the 7400 that effectively lowered the ceiling of the chip to 450 MHz. As a result, all models of the G4 were "speed dumped" in October. The PowerMac G4 PCI was decreased in speed to 350 MHz, for the same $1599 price tag. Existing orders for the G4 PCI/400 were largely honored.
The G4 (PCI Graphics) was terminated at the end of 1999 in favour of a similar configuration based on the G4 (AGP) motherboard.

AGP G4

Announced in September 1999, alongside the PowerMac G4 (PCI Graphics), the PowerMac G4 (AGP Graphics) was a major revision of the PowerMac line. Based on the Unified Motherboard Architecture, The G4 AGP was built around the MPC 7400 chip, which was dramatically faster than its predecessor, the PPC 750.

The G4 AGP introduced a number of performance improvements, including AGP-based graphics, AirPort compatibility, a faster memory bus, DVD-ROM or RAM standard, an internal FireWire port, 2 separate USB buses for a combined 24 Mbs, a 2X (133 MHz) AGP slot, and up to 1.5 GB of RAM. The G4 AGP also introduced the new professional color, "graphite."

The G4 AGP started at £1700 for the 450 MHz configuration with a 20 GB hard drive and 128 MB of RAM, and £2100 for the 500 MHz configuration with a 27 GB hard drive and 256 MB or RAM (both included internal Zip drives).

Not a single first-run G4/500 shipped, and very few G4/450s ever made it to the channel. Orders placed before the speed reduction were honored, with the exception of the 500 MHz orders, which were filled with 450 MHz models with more Memory.
A 350 MHz configuration was subsiquently added to replace the similar G4 (PCI Graphics) configuration a month later, and the whole line was speed-bumped back up to 400/450/500 in February 2000.

Digital Audio G4

With it's built in triclass amp, this mac was targeted at the musician and offered a mac with substantial built in digital audio capabilities. The 466 MHz model shipped with a 16 MB ATI RAGE 128 Pro graphics card and used a PPC 7400 processor. The 533 MHz model used a PPC 7410 processor. The 667 and 733 MHz models used a PowerPC 7450 processor, which included a 256 kB 1:1 on-chip level 2 cache. These models also included a 1 MB Backside level 3 cache, running at a 1:3 ratio to the speed processor. A 32 MB ATI RADEON card was availble on all models as a BTO option. A dual 533-MHz 7410 model was also available BTO. The 733 MHz model included a 24x/8x/4x/6x/2x Combo CD-RW/DVD-R drive. The 667 MHz model was discontinued in March 2001.

Announced in January 2001, the PowerMac G4 (Digital Audio) was the first speed increase for the PowerMac line in over a year. The G4 (Digital Audio) was so-named because of a new Built-in Amplifier, designed to drive USB speakers, along with the conventional minijack line output. The G4 (DA) included a number of architectural improvements, including a 133 MHz bus, 4 PCI slots, and a 1 GB/s main-memory bus. PCI throughput was enhanced by the removal of the PCI bridge (the main memory controller now communicated directly with the PCI bus.). Notably missing from the G4 (DA) was multiprocessing. With the exception of a dual-533 MHz BTO option from the Apple Store, all models included a single processor. This was, according to Steve Jobs, the only way Apple would be able to ship the 667 and 733 MHz models in sufficient quantities.

The G4 (DA) shipped with two new flavors of G4: The low-end models shipped with the PPC 7410 processor, a lower-power variant of the 7400. The higher-end machines shipped with a PPC 7450 processor, which in addition to an on-chip 256 kB L2 Cache, and had four Altivec ("Velocity Engine") units. The PowerMac G4 (DA) shipped in four configurations. All configurations included a CD-RW drive, instead of the DVD-ROM drive of the previous G4 models (DVD-ROM was available BTO). The 733 MHz came with an innovative new "superdrive" which could read and write both CDs and DVDs. It was also bundled with Apple's iDVD, a simple DVD-Authoring application.