PowerMac G4 Upgrades

Configuration

Original

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

• PowerPC Single 450MHz G4 CPU 7400 w/1MB SDR L2 cache
• 100MHz SDR bus w/1GB RAM
• Western Digital 20 GB hard drive
• Onboard ATA/66 hard drive controller
• Pioneer OEM DVR-103 Superdrive
• OEM ATI Rage 120 Pro AGP 16MB graphics card
• Expansion Slots: 3 64-bit 33 MHz PCI, 1 2x AGP
• Mac OS 9.0.4

Upgraded

As of May 2008.

• New exhaust fan
• Pioneer DVR-112 16x Superdrive
• 2x256MB/1x512MB, total 1 GB 100 MHz RAM
• 2x Seagate 80GB 7200 RPM Software Raid 0
• External Western Digital USB/Firewire backup hard drive
• New graphics card fan
• 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.

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 (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 disabled in the Extensions folder or on any boot CDs, else the machine will freeze.

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 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.

• BareFeats MAXPower 7448 vs 7447 vs 7455 vs Core Duo benchmark
• xlr8yourmac PowerLogix 7447A vs 7457 benchmark
• Sonnet 1.7 GHz 7447 vs OWC 1.467 GHz 7455

Candidates

This Sawtooth machines has has these key limitations and requirements to take into consideration before an CPU upgrade:

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

These candidates were available as of May 2008:

1. OWC Mercury Extreme G4/1.467-1.5Ghz 7455B 2MB L3 no-patch needed - $260
2. NewerTech MAXPower G4/7448 1.8 GHz 7448 1MB L2 - $340
3. Sonnet Encore/ST G4 1.8 GHz 7448 512KB L2 - $270