The Power Macintosh G3 was a series of personal computers made by Apple, introduced November 1997. It used the PowerPC G3 (PPC750) microprocessor.

A major leap forward was made in this model through the introduction of a fast, large Level 2 backside cache, running at half processor speed, which reduced data bottlenecks and allowed very efficient use by the computer of its bus speed; 512KB on the 233MHz and 266MHz models, 1MB on the 300MHz and 333MHz models. Because of this, at the time Power Mac G3 machines were widely considered to be faster than Intel PCs of similar CPU speed.

The Power Mac G3 was originally intended to be a midrange series, between the low-end Performa/LC models and the high-end Power Mac 8600 and 9600. During development, it quickly became evident that the G3 was faster machine than the PPC604-based Macs, so the Power Mac G3 became the flagship instead.

The original "platinum" Power Mac G3 series (commonly called "beige G3s") came in two versions: a desktop enclosure inherited directly from the Power Mac 7300, and a minitower similar to (but shorter than) the Power Mac 8600 enclosure. Equipped with a 233, 266, 300, or 333 MHz PowerPC G3 CPU from Motorola, these machines used a 66MHz bus and industry-standard PC66 SDRAM, and were one of the first Power Macs to use IDE hard disk drives.

There were 233, 266 and 300MHz desktop models, and 233, 266, 300, and 333MHz minitower models. The 233 and 266MHz DT models shipped with 4GB HDDs, and the 300MHz with a 6GB drive, all at 5400RPM. The 233MHz minitower shipped with a 4GB drive, the 266MHz with a 6GB drive, and the 300MHz minitower shipped with two 4GB drives; all models were 5400RPM. The 300MHz minitower was replaced by the 333MHz tower, which shipped with a 9GB 7200 RPM SCSI drive, attached to a SCSI/PCI card– also, it had a 100BT ethernet PCI card. Unlike its predecessor, the 300MHz MT, it had only 6MB VRAM, because the 300MHz model shipped with a 128-bit iXMicro PCI video card with 8MB VRAM.

These machines had no audio circuitry on the logic board. Instead, a PERCH slot (a dedicated 182–pin microchannel connector, which is a superset of the PCI spec, but doesn’t accept PCI cards) for a "personality card" was populated with a "Whisper" personality card on regular versions, offering 16-bit, 44kHz audio I/O, or a "Wings" personality card, an AV version which included S-Video capture and output, as well as composite I/Os. DVD-ROM drives were now an available option, and Zip drives continued to be available as well. These machines had onboard SCSI, from the 53C96 SCSI controller, ADB, 10Base-T Ethernet, two serial ports, and onboard ATI graphics (originally Rage IIc, later updated to Rage Pro and then Rage Pro Turbo) with slots for VRAM upgrade. 3 PCI slots and one internal modem slot, as well as 3 SDRAM slots (for up to 768MB RAM) rounded out the features.

Early Platinum G3s with Revision A ROMs do not support slave devices on their IDE controllers, limiting them to one device per bus (normally one optical drive and one hard disk).

The Power Mac G3 (Blue and White) series, introduced in January 1999, was a totally new design. The first new Power Mac model after the release of the iMac, it used a novel new enclosure with the logic board on the "door", which swung down onto the desk for easy access. (This case style was also used on all Power Macintosh G4 models except for the Cube.) These models used the new copper-based PowerPC G3 CPUs made by IBM, which used about 1/4 the power of the Motorola versions. 300, 350, 400, and 450MHz versions were made. The logic board had four PCI slots: three 64-bit 33MHz slots, and one 32-bit 66MHz slot dedicated for the graphics card, an ATI Rage 128 with 16MB SGRAM. Four RAM slots accepted PC100 SDRAM modules, allowing for a maximum of 1GB of SDRAM, running on a 100MHz bus. The onboard IDE was upgraded to Ultra ATA/33, but SCSI was no longer present, having been replaced by two FireWire ports, a new standard (IEEE1394) running at 400Mbps (50MBps). The serial ports were gone, too, having given way to two USB 1.1 ports, as implemented already in the iMac G3. The ADB port remained, as did the option for an internal modem. 100Base-TX Ethernet was now standard, and audio was moved back to the logic board. Zip remained as an option, and some configurations included a DVD-ROM drive and a DVD-Video decoder daughtercard for the graphics card, allowing hardware-assisted DVD video playback. The blue-and-white Power Mac G3 was the first Power Mac with the "New World" architecture based on Open Firmware, as well as the first Mac without onboard SCSI since it was introduced on the Mac Plus. Initially, many buyers chose to buy the older platinum G3s instead, in order to maintain compatibility with existing peripherals.

Early blue and white G3s had IDE controller problems, which make it impossible to connect two hard drives and prevent the use of most hard disk drives produced after them. (Using newer drives in those units results in massive data transmission errors.) The "Rev B" units have a corrected IDE controller which allows two hard disks, and works flawlessly with any drive, within the 28-bit LBA constraint. The Rev B units ship with a hard disk bracket designed for two drives and also have an updated graphics card.

External links

• Pictures of beige desktop G3 and beige minitower G3.
• Pictures of blue and white G3 and some blue and white G3 pictures from Apple.