Cool! Triple- vs double- data rate benchmarks!

[thermodynamic]

http://www.tweaktown.com/articles/1..._analysis_can_dual_channel_cut_it/index7.html

If you have a Pro with all 4 RAM slots used, or a dual quad with all 8 slots used, you're using double-data rate instead of the triple data rate the Nehalem offers. And, best of all, it's by and large immaterial. Synthetic benchmark apps show a big advantage, but real life apps show... well, nothing worth calling mom about...

 

[smacman]

I thought that only the fourth module will be slower when accessed. Not the entire lot of ram. Am I mistaken?

 

[Umbongo]

I thought that only the fourth module will be slower when accessed. Not the entire lot of ram. Am I mistaken?

With this specific situation it changes to interleave across the channels in a dual channel type way. It is supposed to be faster than dual channel would be mathematically, but the numbers give dual channel like speeds on the Mac Pro because there is a futher speed penalty when using more than 1 Unbuffered DIMM on any channel. If (on a 6 DIMM per socket board) you have 2 DIMMs on 2 channels and 1 DIMM on 1 channel, then you (logically) get 3 acting at triple channel speed and the other 2 as dual channel.

 

[Tesselator]

I thought that only the fourth module will be slower when accessed. Not the entire lot of ram. Am I mistaken?

Yes.