Tri-channel memory and the DX58SO

noonand

Looking at building a PC at the moment and the mainboard that I’m looking at is the Intel DX58SO which uses this new feature called tri-channel memory. The Intel Desktop Board DX58SO Product Guide is useful, as p38 of this document goes into some detail:

Optimal memory performance can be achieved by installing three matched DIMMS of equal speed and size in the blue DIMM slots (Channel A, DIMM 0, Channel B, and Channel C) as shown in Figure 18.

It then goes on however to state that:

NOTE
Installing memory in Channel A, DIMM 1 may result in less than optimal memory performance.

Shurely shome mishtake? 8 GB of memory would perform worse than 6GB - I doubt it but can someone who knows let me know?

Gavin Cotter

Basically the way it works is like this.

Channel A, DIMM 0 has wires numbering 0-63 directly to the ram module.
Channel B has wires 64-127 directly to the ram module .
Channel C has wires 128-192 directly to the ram module.

0-63
64-127
128-192

If you add in a fourth memory module there's no wires directly for 193-254 as the wires only go up to 192 so it shares the other ones wires.
Thats what causes the slow down.

Ddr3 memory is 64bit so 3 * 64 is 192bit thus your increased performance with tripple channel as opposed to say dual channel 128bit.
Hope that made it a bit easier, if not just ask.

noonand

Gavin,

Thanks very much for your kind reply - I appreciate it.

However if I have 6GB of memory (of the correct kind) and add in another 2GB will I see a marked decrease in performance?

Gavin Cotter

Realistically speaking,you won't notice it at all.Dual channel memory is more than enough with the Core i7.
Your welcome.

noonand

Gavin,

Thanks very much - appreciate all your help!