[cdhostage]

When the G5 is updated, presumably next Spring, Apple will be setting a new record for personal computer bus speed. Assuming it's kept running at half the proc speed, the bus will be going at nearly twice the rate of Intel chipsets. Yeesh, a 3 dual 3 GHz G5 video editing station. Thank God for the Lottery.

The best G4's bus speed was 167 MHz. How can the G5's bus be running so much faster (500x2?)
Looking it over, I realize that I don't know exactly what this "system bus" connects to. The main RAM is another step or two away through the memory controller and Northbridge. This 1 GHz system bus speed, what exactly does it refer to?

[Spliffdaddy]

A 'system bus' carries data between the processor, I/O, and memory.

The speed of the 'memory bus' CAN BE different than the speed of the 'system bus'. The same is true of I/O bus speeds. It's confusing because you're accustomed to seeing the same speed for both system bus and memory bus.

With a G5 - For tasks not requiring the use of RAM, a fast system bus is, um, faster at moving the data.



PS, don't quote me on this:

I would think that in multiprocessor configurations you would need as much bandwidth as possible in the 'system bus' in order to efficiently link between the CPUs as well as their own memory and I/O busses. Ideally, I suppose, you would want 2X the 'system bus' bandwidth necessary for a single CPU.

Those cheap supercomputer clusters made from multiple PCs are linked together via I/O bus-interfaced expansion cards. The bandwidth available is meager. Real supercomputers have adequate bandwidth between CPUs - and better performance. Look for the bottleneck. It's always there. More is better.

[zac4mac]

Dig around the Apple site for the tech specs of the G5 system. There's a PDF with all the pertinent poop at -
http://a448.g.akamai.net/7/448/51/df..._TO_072903.pdf

Processor to controller - 2 way up to 1 GHz
memory to controller - interleaved DDR400(200 MHz double-pumped and interleaved)for an effective RAM speed of 800 MHz
Controller to AGP 8x at 533MHz

[mac freak]

Redonkulous! AWESOME FREAKIN' WORD!