PowerMac G4 Upgrades

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PowerMac G4 sawtooth.jpg
How to upgrade a PowerMac G4 450 MHz Sawtooth purely running Mac OS 9.

Hardware configuration

This is one of the first PowerMac G4 machines, with the new PowerPC G4 7400 processor and AGP 2x, nickname "Sawtooth" released in 1999.

This machine works as a Xerox printer rip and workstation, featuring dual Xerox 64-bit PCI printer controller cards. As this is a production machine every upgrade has to be thoroughly tested and easy to replace if an issue crops up. The Xerox Splash printer server software is only available for Mac OS 9.


  • PowerPC Single 450MHz G4 7400 w/1MB SDR 2:1 225MHz L2 cache
  • 100MHz SDR bus w/2x256MB, 512MB total RAM
  • OEM Western Digital 27 GB hard drive
  • Onboard ATA/66 hard drive controller
  • OEM Pioneer DVD-RAM drive
  • ZIP drive
  • OEM ATI Rage 120 Pro 16MB SDRAM 2x AGP DVD/VGA graphics card
  • Expansion Slots: 3 64-bit 33 MHz PCI, 1 2x AGP
  • Mac OS 9.0.4


As of May 2008.

  • 2x256MB 1x512MB, total 1 GB 100 MHz SDR RAM
  • New exhaust fan
  • New graphics card fan
  • 2x Seagate 80GB 7200 RPM hard drives - SoftRaid Raid0
  • External Western Digital 500GB USB/Firewire backup hard drive
  • Retail Pioneer DVR-112 18x IDE Superdrive
  • Mac OS 9.2.2

CPU Upgrade

There are several CPU upgrades available for the PowerMac G4 line. The CPU die is located on a daughterboard and socketed onto the motherboard, fastened with 3 screws. Upgrading the CPU requires only removal of the heatsink and the screws.

PowerPC G4

The PowerPC G4 microprocessor was a collaboration between Apple, IBM, and Motorola (Freescale). During its lifespan it evolved from clock speeds ranging from 350 MHz up to 2.0 GHz (overclocked 1.6GHz).

  • PowerPC 7400 - 1MB L2 - 200nm
  • PowerPC 7410 - 1MB L2 - 180nm
  • PowerPC 7450 - 256KB L2 - 2MB L3 cache - 180nm
  • PowerPC 7445 - 256KB L2 - 180nm
  • PowerPC 7455 - 256KB L2 - 2MB L3 cache - 180nm
  • PowerPC 7447 - 512KB L2 - 130nm
  • PowerPC 7457 - 512KB L2 - 2MB L3 cache - 130nm
  • PowerPC 7448 - 1MB L2 - 90nm

For more details, see the PowerPC G4 article on Wikipedia.


There are several manufacturer of CPU upgrade boards for the PowerMac G4.

Upgrade boards

All the latest upgrades based on 7447, 7457, 7457, and 7448 all require an initial firmware patch by holding the programmer button and boot a CD to patch the NVRAM. The patch includes 7457/7447A/7448 enabler patch, PLL patch for correct System Profiler speed report, L3CR extended ratios patch to correct L3 cache ratio above 6:1, and thernal fan control [1]. Also the CPU Plugins extensions has to be disabled in the Extensions folder or on any boot CDs, or else the machine will freeze before the desktop loads.

Fortunately, boards based on 7455 does not require any patching or special handling, and can be used as a straight drop-in replacement.

7448 vs 7455 performance

The latest 7447/7448 processors doesn't include a L3 interface, only the slightly older 7455/7457 has a 2MB L3 cache. Benchmarks shows that a 7455 1.42 GHz can outperform or equal a 7448 1.8 GHz on numerous tests almost solely because of the extra L3 cache, especially earlier machines that has slow bus/memory speed and with throughput intensive applications (e.g. Sawtooth and Photoshop) can get an advantage of the L3 cache. Althought the 7455 is older and runs hotter because of the 180 nm vs 130 nm manufacturer process, the 7455 based CPU upgrades usually sells for much less than the newer 7448 boards.

OWC G4 CPU Upgrade
FastMac G4 CPU Upgrade
NewerTech G4 CPU Upgrade

Upgrade candidates

This Sawtooth G4 has has several key limitations and requirements that has to be taken into consideration before an CPU upgrade:

  • 100 MHz system bus
  • Uni-North (Uni-N) ASIC bridge chip (Northbridge) revision: 3 (dual processors require revision 7 or later, found March 2000 and later)
  • Firmware 4.2.8 (latest)
  • Production workstation

These candidates were considered and available as of May 2008:

  1. OWC Mercury Extreme G4/1.467GHz-1.5GHz - 7455B - 256KB 1:1 L2 cache - 2MB SDR 233 MHz 6:1 L3 cache - manual - no patch or extension removal needed - $260
  2. FastMac 1.467-1.5 GHz - 7455 - 256K 1:1 L2 cache - 2MB SDR L3 cache - manual - no patch or extension removal needed - $260
  3. NewerTech MAXPower G4/7448 1.8 GHz - 7448 - 1MB 1:1 L2 cache - manual- $340
  4. Sonnet Encore/ST G4 1.8 GHz - 7448 - 512KB 1:1 L2 cache - $270

The OWC Mercury tops the list because of the easy installation without the need to patch and remove extensions, L3 cache advantage on Macs with slower bus speed vs higher clock speed, great value for performance, clean install fan plugs onto board, and great OWC reputation and support.

Dual processors upgrades are out because of the incompatible Uni-North bridge chip.


These utilities lets you view system details and sometimes configure the CPU upgrade (manufacturer dependant).


Video card upgrade

The ATI Rage 128 Pro with 16 MB VRAM isn't capable of driving a new 22-inch widescreen 1680x1050 LCD monitor. Replacing the card isn't as simple as finding a new AGP graphics, although the hardware can be the same for PC and Mac, the firmware driving the card has to be made specially for the Mac.

There are new ways to flash a regular Geforce and Radeon video card with a new flash ROM to make it work with a Mac, but these methods are highly experiemental and not suited for a production machine. More Geforce flash and ATI mod details.

Upgrade candidates

As this PowerMac still has to run Mac OS 9 the new video card preferably should have native OS 9 driver support and 3d acceleration.

  • Drive 1680x1050 32-bit resolution
  • Mac OS 9 native support
  • Sawtooth 2x AGP compatible

All of the cards listed below is only available as refurbished and used from other PowerMac G4 models. All cards from PowerMac Sawtooth, Gigabit, Digital Audio, Quicksilver and Mirror Drive Door, FW800 should work with earlier PowerMacs, i.e Sawtooth 2x AGP [2].

Reportedly the Radeon 9700 and up GPUs will not have OS 9 driver support for 3D/OpenGL acceleration [3].

Considered candidates as of May 2008:

  1. ATI Radeon 9000 Pro - ADC/DVI - 2x 4x AGP - Fanless - 1680x1050 confirmed [4] - Excellent replacement - $120
  2. ATI Radeon 8500 - DVI/VGA - Fanless - Some only with VGA - $113
  3. Nvidia Geforce 4 Titanium - ADC/DVI - Unsharp on CRT(?) [5] - Fastest available for OS 9 w/3d acceleration - $133
  4. ATI Radeon 9200 - Lower 3D performance - $108
  5. ATI Radeon 9800 Mac - No acceleration in OS 9 - Extra auxiliary power needed - $174
  6. Nvidia Geforce MX4 - ADC/DVI

Detailed specifications for the preprocessing units:

Resellers of old Mac video cards can be found on Ebay, e.g. local338 and applemacanix.


Hard drive upgrade