Getting the Most from Your Power Mac G5

The PowerPC platform had a long life at Apple. The first Power Macs arrived on March 14, 1994 – the Power Mac 6100, 7100, and 8100 running the PowerPC 601 CPU at speeds of 60, 66, and 80 MHz respectively. The ultimate Power Mac was the G5 Quad, which had two 2.5 GHz dual-core CPUs and arrived in October 2005.

In June 2005, Apple shook the Macintosh world by announcing that it would switch from PowerPC chips to Intel x86 CPUs “within a year”. Those of us using Macs were stunned. Apple had long touted the advantages of its PowerPC RISC CPUs against Intel’s x86 architecture. Now it was poised to follow the road more traveled.

Apple didn’t quit introducing new PowerPC models right away. After all, we pretty much assumed the Intel transition wouldn’t take place until June 2006. It came five months before that, but that didn’t keep Apple from introducing one last generation of G5 Macs in late 2005.

The Power Mac G5

Power Mac G5The first Power Mac G5s arrived in June 2003 with speed ranging from 1.6 to 2.0 GHz. This compares favorably with the fastest Power Mac G4 ever, the dual 1.42 GHz FireWire 800 model that had been introduced that January. That top-end Power Mac G4 achieves a Geekbench 2 score of 1224. The dual 2.0 GHz Power Mac G5, Apple’s new top-end model, eclipses that with a score of 1692 – 38% higher than the G4!

A number of factors contribute to this improvement. The top-end G5 clock speed is 40% faster. The memory bus runs at 1.0 GHz vs. 167 MHz – six times as fast. The G4 has a 64 KB Level 1 cache and a 256 KB Level 2 as part of the CPU plus a 2 MB Level 3 cache. The G5 has a Level 1 cache with 64 KB for instructions and 32 KB for data as well as a 512 KB Level 2 cache on the CPU, with no need for Level 3 since the memory bus is so fast. And the G5 is a 64-bit CPU, the first to find its way into a personal computer.

The 1.5 GB/s SATA drive bus is 50% faster than Ultra ATA/100 in the G4. Where the G4 uses regular 33 MHz 64-bit PCI expansion slots, the 1.8 and 2.0 GHz G5 models embrace PCI-X and have 100 and 133 MHz 64-bit slots. And where the last Power Mac G4 supports up to 2 GB of memory, the PCI-X G5 models can handle a whopping 8 GB.

Curiously, all Power Mac G5 models use Ultra ATA/100 for their optical drives rather than SATA.

For expansion, the Power Mac G5 uses USB 2.0 instead of the lazily slow USB 1.1 found in all G4 Power Macs, and it has a USB port and a FireWire 400 port up front for easy access, as well as a headphone jack.

The PCI Models

In each generation except for the last one, Apple included a low-end Power Mac G5 with old-fashioned PCI expansion slots and a 4 GB memory ceiling – still twice as high as the Power Mac G4. In the first generation, it was a single-processor machine.

All G5 Power Macs prior to the Late 2005 models use the same power supply, which can get dusty, overheat, and die. It can be cheaper to buy a used PCI G4 for its power supply than buying the power supply separately.

Getting Faster and Faster

In June 2004, the entry-level Power Mac ran at 1.8 GHz, while the top-end model hit 2.5 GHz – a 33% higher clock speed plus a second processor! All models introduced in June 2004 had dual processors.

Apple pushed forward, as did IBM, the manufacturer of the G5 CPU, and in April 2005, Apple announced the third Power Mac G5 generation with speeds ranging from 2.0 GHz to 2.7 GHz, which was the highest clock speed any PowerPC Mac ever achieved, although Apple did so by overclocking a 2.5 GHz CPU to 2.7 GHz. Once again, every new model had dual processors.

The Final Generation: Dual-Core Processors

IBM improved the G5 with a dual-core chip, and the October 2005 models all use it. The entry-level machine runs at 2.0 GHz, the midrange at 2.3 GHz, and the top-end has two dual-core CPUs running at 2.5 GHz, making it hands down the most powerful PowerPC Mac ever.

Where the 2.7 GHz dual processor model has a Geekbench 2 score of 2259, the 2.3 GHz dual-core model benchmarks just 8% slower, while the G5 Quad “killed it” with a score of 3316.

When Apple made the switch to Intel, every model until the first Mac Pro had lower Geekbench 2 scores than the Power Mac G5 Quad. The 2.3 GHz G5 Dual scores 2082, comparable to a 1.66 GHz Core Duo CPU in a first-generation Intel Mac. The 2.5 GHz G5 Quad scores 3316, roughly equivalent to a 2.4 GHz Core 2 Duo-based Mac. The original low-end 2.0 GHz 4-core Mac Pro scores 4032, only 22% faster than the G5 Quad.

The dual-core Power Macs have a 1 MB Level 2 cache, twice as large as earlier G5s, and the memory ceiling jumps to 16 GB. For expansion, Apple adopted PCI Express (a.k.a. PCIe). This was the only Power Mac G5 generation to use PCIe for its video card instead of AGP, and as the only PowerPC Mac with PCIe video, it can be challenging to find supported cards if you want to update to a more powerful GPU.

Expansion Options

Hard Drives and SSD

All Power Mac G5 models have two SATA buses and officially support two SATA hard drives, although there were some third-party options for adding even more drives. For real power users, the Sonnet G5 Jive (discontinued) provided room for three hard drives. You will need to add a SATA card to your Power Mac G5, as the built-in SATA controllers can only handle two drives.

Bear in mind that you cannot use hard drives larger than 2 TB with any PowerPC Mac. This is a limitation of the Apple Partition Map (APM), which is required on any drive that will boot a PowerPC Mac. This applies equally to internal drives, SCSI drives, USB drives, FireWire drives, eSATA drives, and even shared Mac volumes on your network.

For all-out speed, you can use a Solid State Drive (SSD), and its performance will only be limited by the speed of the Power Mac’s 1.5 GB/s SATA bus. Adding a 3.0 GB/s SATA Rev. 2 card is an option. Site sponsor OWC has offered these cards. Prices for cards that have not been discontinued are as of March 19, 2018:

For PCI and PCI-X Models

  • 1.5 GB/s Sonnet Tempo PCI/PCI-X host adapter, $59 (disc)
  • 1.5 GB/s FirmTek SeriTek/1eVE4 PCI/PCI-X external SATA host adapter, 4 eSATA ports, $137.99 (disc)
  • 3.0 GB/s FirmTek SeriTek/2SE4 PCI-X external SATA host adapter, 4 eSATA ports support up to 20 drives, $179 (disc)

For Dual-Core Models

  • 3.0 GB/s Sonnet Tempo SATA E2P host adapter, 2 eSATA ports, $48.79
  • 6.0 GB/s Sonnet Tempo SATA Pro 2 host adapter, 2 eSATA ports, $29 (disc)
  • 6.0 GB/s NewerTech MAXPower PCIe eSATA, 2 ports, eSATA only, $39.75
  • 6.0 GB/s OWC Accelsior S, dual-lane, supports a single 2.5″ SSD, $49.99
  • 6.0 GB/s NewerTech MAXPower PCIe 4-port eSATA 6G RAID, eSATA only, $79.75
  • 6.0 GB/s FirmTek SeriTek/e6G host adapter, 2 eSATA ports support up to 10 drives, $97.99 (disc)
  • 6.0 GB/s Sonnet Tempo SSD, mount 1-2 2.5″ SSDs, $118.99
  • 6.0 GB/s OWC Mercury Accelsior E2, SSD plus 2 eSATA ports, $144
  • 6.0 GB/s FirmTek SeriTek/6G2+2 2.5″ SATA/eSATA Host Adapter, supports 1-2 2.5″ SSDs, adds 2 eSATA ports, $197.99
  • 6.0 GB/s Sonnet Tempo SATA Pro 4 host adapter, 4 eSATA ports, $199
  • 6.0 GB/s Sonnet Tempo SSD Pro Plus SATA PCIe SSD host adapter, supports 2 2.5″ SSDs and has 2 eSATA ports, $267.99.

OWC prices for 6.0 GB/s SATA Rev. 3 SSDs start at $48.


We used to say that you can never have too much memory, but there’s no point paying for more memory than you could possibly need.

Here are current (March 2018) prices from OWC:

  • Single G5, 2 x 1 GB: $19, can take 2 kits
  • Dual G5, 2 x 1 GB: $19, can take 2 kits
  • Dual G5, 2 x 1 GB: $19, can take 4 kits
  • Dual-core G5, 2 x 2 GB: $35.75 can take 4 kits

Make Your Choice

I’ve had several Power Mac G5 models. The 2.3 GHz dual processor model was quite loud, and the 2.3 GHz dual-core model that replaced it is very quiet. I’ve heard lots of stories about problems with liquid-cooled models, but I have no hands-on experience with them. The G5 Quad has a reputation for reliability that the 2.5 and 2.7 GHz liquid cooled models don’t have.

These remain very capable computers. They can all run Mac OS X 10.4 Tiger and 10.5 Leopard. Leopard is more modern, wants more memory, and has some features that integrate it with Intel Macs better than Tiger does. Tiger needs less memory to run smoothly and is the last version of OS X to include Classic Mode, which lets you run old Mac OS 9 software.

If you have an ADC display, only the PCI and PCI-X models include an ADC port on their video cards, alongside a DVI port. The Late 2005 dual-core models have two DVI ports and require Apple’s expensive DVI-to-ADC adapter to support an ADC display.

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