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 The Source for Mac Performance News and Reviews Don't forget to check out all the other site features! A Peek at the Apple Sawtooth (G4/450 AGP System) CPU Module | |||||||||||||||||||||||||||||||||||||||
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The Apple G4/AGP systems introduced in Fall 1999 (code named "Sawtooth") have a different motherboard and CPU module design than the previous B&W G3 and PCI based G4 ("Yikes") models. The Sawtooth design includes an AGP graphics card slot, internal Firewire port, dual USB controllers (independent of each other), Airport wireless networking card slot/antenna and a non-ZIF socketed CPU module. (I'm pretty positive there will be Sawtooth CPU upgrades however.) Many readers had expressed interest in seeing what's under that huge heatsink so I'm posting this to answer those requests. It's humbling to compare the B&W G3 heatsink to the G4 version as the photo below shows. Don't worry - the G4 heatsink may be 4 times as large, but the chip is only about twice as hot according to the chip specs (shown below). Based on what I've seen with G4 CPU upgrades, I think the G3 spec must be low, as I don't think the G4 is actually twice the wattage of the G3.
 B&W G3 vs G4 Heatsink As you can see in the image above - the G4's heatsink is massive, however it never seems to get the least bit warm. I can only guess that Apple provided for the day when there would be two G4s on the module (there appears to be room, if the board had a relayout of components). The existing heatsink would need to be modified for two G4s however, as there is currently a single raised contact 'block' on the back of the heatsink for the CPU. Future G4s will eventually be lower voltage (dissipating less heat), perhaps enough that by next summer there may be the possibility of a G4 Powerbook. The specs on the current G4/450 shows an 8.9W typical, 16.5W maximum rating (a 400MHz Motorola G3 rates 4.8W/8.0W respectively). Again, I think the Motorola G3 chip may be nearer to 8W typical in my opinion.
 Sawtooth CPU Module Note the single cache chip on this side (another one is on the bottom side of the module). With a relayout, I think there is space on this module for two G4 CPUs. Technical Details/Speed Control Configuration: For a reference only (don't try this at home) page outlining the Bus ratio (Bus/CPU multiplier), Core Voltage, L2 signal level and Bus Clock (PCI/AGP) timing info, see Michiro Isobe's Sawtooth CPU module details article published here.
PowerPC 7400/G4 Specs: Based on Motorola info as of late August. 500MHz and faster versions due (in mass) early next year. My sources indicate it may have a 10x or 12X bus/CPU ratio. All specs subject to change of course.
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