Author Topic: The Power Mac G4 Desktop family in brief.  (Read 2641 times)

Offline MacTron

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The Power Mac G4 Desktop family in brief.
« on: December 05, 2015, 06:42:39 AM »
From August 31, 1999 to June 9, 2004 the Power Mac G4 was the king not only in the Apple models line but in the whole personal computer scene. During this almost 5 years of reign the software take a lot of optimizations for the G4, whereas this CPUs suffered some inner evolution, and a Mhz speed increase.
Here I will try to show in brief some differences in the G4 desktop line and in the - very important and less known - evolution on this machines in the motherboard side.

The HD 48-bit support means that the ATA port is capable of using hard drives size over 128GB natively.
The 24v display means that the motherboard and the power source supply 24 volts to feed a monitor, usually an Apple Cinema Display.

Even the AGP Graphics (Yikes), AGP Graphics (Sawtooth and Gigabit Ethernet) and Digital Audio have the same case, the differences between them can be observed in the rear side:

Unless you already have it, don't buy the Yikes G4, because it's a G4 in a G3 motherboard.

The Sawtooth it's the G4 easiest to maintain because it can use a lot of PC pieces, with few modifications ( power source, video card ... )

In the upper picture we can see a diagram of the main motherboard layout.

In the Yikes a lot of devices share the same PCI bus, ( including the graphics card) dramatically reducing the performance of the whole system.

In the Sawtooth the Firewire, Ethernet and Graphic Port (now AGP) are directly derived from the UniNorth, increasing the overall system performance whereas the PCI only have to support the ATA bus (now ATA 66) , letting free more PCI bandwidth for user installed cards.

The G4 Gigabit Ethernet is identical to a Sawtooth but with some improvements on the UniNorth that - as its name implies - allow the ethernet to work at Gigabit speed.

The QuickSilver and the Digital Audio have the same motherboard, with some improvements respect to previous models. Mainly system bus is raised to 133 Mhz and the AGP is now 4X. The late QuickSilver models include native support for large HDs.
In both systems the system bus can be overclocked to 150 Mhz.

The G4 MDD is the powerful of the family -the 166 Mhz system bus models-.
A very improved and different UniNort is used, that's why CPU modules for this machine are incompatible with CPU modules from previous G4s.
The system bus protocol is better and faster (166 Mhz), the RAM bus is now DDR, the ATA bus is now directly supported by the UniNorth ( 66 Mhz inner PCI BUS) and upgraded to ATA 100. Letting free a lot of bandwidth from the PCI BUS for user installed cards.
And even though the G4 CPU doesn't support DDR, the DDR extra bandwidth allow greatly benefits all Direct Memory Access (DMA) processes, noticeably the AGP graphic card memory mappings.

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