Two Dual Channels

A number of people asked basically the same question, “What’s the difference between the Canterwood/Springdale boards and the dual-channel nForce2 Athlon board? Isn’t what you say about the first applicable to the second, too?”

The answer is, “No, they aren’t alike insofar as this issue is concerned, because the PIV and Athlon buses are different.”

The Athlon bus is a dual pumped bus. That’s a fancy way of saying that it can pump two signals per clock cycle.

The PIV bus is a quad-pumped bus. That’s a fancy way of saying that it can pump four signals per clock cycle.

This means at the same MHz frequency, the PIV bus will always have twice the FSB bandwidth of the Athlon bus.

For instance, at 200MHz, the PIV bus will have a maximum FSB bandwidth of 6.4Gb/sec; while the Athlon’s maximum FSB is 3.2Gb/sec.

When you remember that a single DDR400 memory module can provide 3.2Gb/sec all by itself, you can see that a dual-channel Athlon system provides far more bandwidth than the Athlon bus can conceivably handle.

While you get a little improvement using dual-channel rather than single-channel in the nForce2 board, this is really more filling in any available room in the cramped Athlon FSB highway than any new capacity.

So the discussion on moving the PIV FSB even further out (and expands the length of the highway) really isn’t applicable to nForce2 boards because the Athlon highway is and can only be half the width of the PIV highway, and you can never arrange things so that you’ll have plenty of room for both dual-memory and everything else.


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