New MP Ram Question

[JustinBW]

I just got a new Mac Pro. I got the baseline quad and looking to upgrade the ram, but I am unsure about whether I need to do it in pairs, 3s or it doesn't matter.

I am getting some conflicting opinions on it. The apple.com guy said he had no specs on it and theorized that I had to do it in 3s. Crucial told me it didn't matter ( I could do it in pairs, 3s or whatever I want).

Does anyone have any definitive answers?

Thanks a ton.

[2contagious]

Diglloyd from macperformanceguide.com answered to my eMail a while ago saying this:

I've run it with 1/2/3/4 modules (8GB). All combos work fine.
Bandwidth with 1 module is poor, about 1/3 that of max.


So yeah.. apparently it's possible to run it with 1, 2, 3 or 4 modules installed. This was tested with 8GB RAM sticks from OWC on a hexacore Mac Pro 2010. RAM performance will be poor with only 1 stick installed though.

[sboerup]

It's best in pairs of 3, but will work fine with just 2. You're not going to feel a difference though, but the pairs of 3 is best.

[JustinBW]

It's best in pairs of 3, but will work fine with just 2. You're not going to feel a difference though, but the pairs of 3 is best.

Im confused, pairs of 3? 6 in total? or sets of 3?

I think you mean sets but I want to be sure.

[xgman]

sets of 3, (so either 3 or 6 if your board has 6) all matching size and manufacturer if possible.

[reekster]

From what I found out, the Westmere 6 core can access a triple thread of memory, hence the configuration of three memory modules in some of the stock builds. When you install 4, it breaks it up into two sets of double threads which I'M TOLD is a little slower. I haven't tested that theory but have asked to different techies and read up a bit about it so that's my assumption.

[Ravich]

It is the same for the 2009 Mac Pros, and the general consensus is that RAM modules are so big these days that adding a 4th stick is pretty much always going to increase performance because of how much extra memory you're getting, despite the fact that it switches from triple channel to dual.

[JustinBW]

Thank you all for the replies!