Mac Pro (Nehalem, 4,1) Memory Upgrade

[funkahdafi]

Hi,

I have the Nehalem Mac Pro (I think it's 2009? MacPro4,1) with Quad-Core processors. Currently I have 6 of the 8 available memory banks deployed with a total of 12 GB Ram.

Now I need more. But as far as I remember, the Nehalem memory architecture runs best if memory is deployed in members of three banks (like 2 * 3 * 6 GB).

What would happen if I use the fourth banks? Would I see a performance drop?

Thanks

 

[SuperJudge]

Nope. More memory trumps less memory.

 

[Hellhammer]

More memory will nearly always yield a higher performance than dual- or triple-channeling setups would. Only very few apps can take advantage of such high memory bandwidths. Just get more memory and fill the remaining slots

 

[funkahdafi]

Ok, thanks.

Say all my banks are filled with 2 GB modules. Would it be possible to put 4 GB modules in the remaining two slots?

And while we are at it, what kind of memory do I need exactly for that model?

Thanks!

 

[Hellhammer]

Yes, you can use 4GB modules. You could check OWC, TransIntl and Crucial, they sell RAM that works in Mac Pros

 

[DeeEss]

even if you follow the triple channel theory the difference in performance hit is something as little as 1 or 2%

 

[funkahdafi]

All right, you got me sold, I am going to upgrade.

The question that still remains: What RAM modules exactly do I need? I know where to buy it, but I need specifications.

Thanks again!

 

[Hellhammer]

All right, you got me sold, I am going to upgrade.

The question that still remains: What RAM modules exactly do I need? I know where to buy it, but I need specifications.

Thanks again!

DIMMs for Mac Pro (Early 2009) must fit these specifications:

• PC3-8500,1066MHz, DDR3 SDRAM UDIMMs
• Error-correcting code(ECC)
• 72-bit wide, 240-pin ECC modules
• 18 memory ICs maximum per UDIMM

http://manuals.info.apple.com/en_US/Mac_Pro_2009_2010_Memory_DIMMs_DIY.pdf

 

[funkahdafi]

Hellhammer, you rock!

Thanks mate!

 

[funkahdafi]

Actually I have more questions:

As I said, I currently have 6 * 2 GB, spread across slots 1-3 of each memory riser.

Regarding to a FAQ here on MacRumors, I should install matching PAIRS:

"The RAM must be installed in matching pairs, in this order: Riser A slot 1&2, Riser B slot 1&2, Riser A slot 3&4, Riser B slot 3&4."

Are you guys sure I can put 4 GB modules in the remaining slots? My understanding of this FAQ (while english not being my native tounge) is that I have to put the same size modules in slot 3&4. Since 3 is already loaded with a 2 GB module, I am kind of nervous buying 4 GB.

 

[funkahdafi]

forget it.. just called apple (I have apple care). regarding to the guy, my remaining slots nr. 4 and nr. 8 would form a pair, so the 4 GB modules in there should work.

 

[Hellhammer]

In the past, memory had to be installed in pairs but that is not the case anymore. It will work fine. Also:

If you install different-size DIMMs in your computer, follow the order in the tables above. If the DIMM configuration you install doesn’t provide optimized performance, the Memory Slot Utility will appear on screen and recommend an improved configuration. To use the Memory Slot Utility again, go to /System/Library/Core Services.

From the link I posted above.