Power Macintosh G3 - Hardware

Hardware

The beige Power Macintosh G3 series came in three versions: an "Outrigger" desktop enclosure inherited directly from the Power Macintosh 7300 (and ultimately derived from the Macintosh IIvx); a minitower similar to (but shorter than) the Power Macintosh 8600 enclosure; and a version with a built in screen, the G3 All-In-One ("AIO"), sometimes nicknamed the "Molar Mac" due to its resemlance to a tooth, that was made available only to educational markets. Equipped with a 233, 266, 300, or 333 MHz PowerPC 750 (G3) CPU from Motorola, these machines used a 66.83 MHz system bus and PC66 SDRAM, and standard ATA hard disk drives instead of the SCSI drives used in most previous Apple systems; however, they retained a legacy Fast SCSI internal bus (up to 10 MB/s) along with the then-standard DB-25 external SCSI bus which had a top speed of 5 MB/s. Each bus could support a maximum of 7 devices.

The G3 used Apple's new "Gossamer" logic board, which had originally been developed with an eye towards maximum compatibility with PC components. This was known as the "Yellowknife" project, which had sought to develop the first Apple RISC product — capable of running any OS that would support it, be it Mac OS or Windows. It was an effort by Apple to gain market share, by allowing their hardware to run industry-standard software, but still remaining Mac OS proprietary. The prototype had a ZIF-socket G3 processor, PCI and ISA slots, Mac and PC serial ports, onboard SCSI, PC and Mac floppy drive connectors, ATX power supplies, and PS/2 keyboard and mouse connections, inserted into an ATX case. The project was scrapped by Steve Jobs, after his return to Apple, and his realization of the devastation of Apple's profits due to the Clone makers. Remnants of this effort can be seen in the form factor of the production G3: the logic board's similarity to the PC ATX motherboard standard; solder points for a PC-type floppy drive; and the ability to use both proprietary Apple power supplies and industry-standard ATX power supplies. As a compact and versatile motherboard, the Gossamer board was originally designed to be able to support both the high-end PowerPC 604e and the new PowerPC G3, but when initial tests found that the cheaper G3 outperformed the 604e in many tests, this functionality was removed and Apple's 604e-based systems died a quiet death.

These machines had no audio circuitry on the logic board; instead, a PERCH slot (a dedicated 182-pin microchannel connector; a superset of the PCI spec, but which does not accept PCI cards) was populated with a "personality card" which provided the audio circuitry. Several "personality cards" were available:

• Whisper was the personality card of the regular versions, providing the Screamer sound ASIC (with 16-bit, 44.1 kHz audio capabilities with simultaneous I/O) and no video facilities.
• Wings or Audio/Video Input/Output Card was an A/V "personality card" which, in addition to the audio I/O, included composite and S-Video capture and output.
• Bordeaux or DVD-Video and Audio/Video Card differed from the Wings card in that it did not include a DAV slot, used the Burgundy sound ASIC (which provided improved sound performance), incorporated a higher performance video capture IC, and included additional circuitry (C-Cube MPEG decoder chip) to support the playback of DVD movies.

DVD-ROM drives were now an available option, and Zip drives continued to be available as well.

These machines had onboard and external SCSI (from the custom MESH IC), ADB, 10BASE-T Ethernet, two MiniDIN-8 serial ports, and onboard ATI graphics (originally IIc, later updated to Pro and then Rage Pro Turbo) with a slot for VRAM upgrade. Three full-length PCI slots and one internal modem slot, as well as three SDRAM slots (for up to 768 MiB RAM) rounded out the features.

The G3 was the last desktop Macintosh to include built-in external serial ports.

Early 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). Additionally, they came with onboard ATI Rage II+ video. G3s with Revision B ROMs support slave devices on their IDE controllers, and had the onboard video upgraded to ATI Rage Pro. G3s with Revision C ROMs also support slave devices on their IDE controllers, but the most significant technical differences are the newer Open Firmware version than the previous two models (2.4 vs 2.0f1) and another onboard video upgrade, this time to ATI Rage Pro Turbo.

The G3 was the last Power Macintosh with a 4 MB ROM. The trend of increasingly large ROMs ended after the introduction of the New World ROM in the iMac, and then the B&W Power Macintosh G3.