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Dual Channel Memory

Owners of AMD systems with a 400MHz FSB can be satisfied that they're getting the maximum potential out of their PC3200 DDR RAM. Afterall, a 64 bit FSB running at 400MHz has a theoretical maximum bandwidth of 3.2GB/sec. This happens to be the same bandwidth as the PC3200 RAM.

But what happens if you've got an Intel P4 system with an 800MHz FSB (which is actually a quad-pumped 200MHz bus)? The FSB is now capable of a whopping 6.4GB/sec, but - alas - your RAM is not. The RAM therefore becomes a system bottleneck.

And so we come to dual channel memory. Recognising this system bottleneck, modern systems have been designed with memory controllers with two 64 bit channels. So long as you pair your RAM DIMMs and put them in the right slots, RAM bandwidth is doubled! Couldn't be easier. And what's more... The RAM itself is identical. I.e. you don't need to purchase 'special' PC3200 RAM. The only difference is the architecture of the memory controller.

If you put two sticks of PC3200 RAM into a board that supports dual channel memory, then you can have a full 6.4GB of bandwidth (assuming your FSB is fast enough).

What's next

The next section looks at some of the other types of memory found in PCs today: the various types of ROM and Virtual memory.