Ram and Slots (Nehalem 2009)

Hi-

Yes, it's true.

Running memory in the Nehalem MP in threes is the preferred method for maximum performance.
http://www.barefeats.com/nehal04.html

Running 12GB RAM at 6x 2GB is optimal for the triple channel controller.

Note on page 4 of the Apple memory installation guide, that filling channels 1,2,3 and 5,6,7 (balanced across channels) is recommended for best performance.
http://manuals.info.apple.com/enUS/Mac_Pro_Early2009_Memory_DIMMDIY.pdf

No worries! 🙂

I'm confused. I have the 8 core which came
with 6 gb of memory (6-1gb cards)

The remaining two slots are open, can I add memory to these slots? I get the impression I cannot unless it matches the 1 gb cards??????

Hi-

The current configuration will provide optimization of the three channel memory controller.

can I add memory to these slots?

You can add 2 more 1GB DIMMs if you like.
Chances are that you will not notice any slowdown in real world use, even though benchmarks may show otherwise.

Another way to put it is, if you need more memory, add it.
However, keep the memory configuration balanced.

Than adding 2gb cards to remaining two empty slots would be wrong? I would have to add only 1 gb cards, is that correct?

thx

Than adding 2gb cards to remaining two empty slots would be wrong?

Not necessarily wrong, just not optimal.
If the two DIMMs were 4GB each, then "wrong" would be correct.

You can install different sized DIMMs, but if the Memory Slot Utility tells you to change the configuration, follow the instructions.

For the two additional 2GB DIMMs, slots 4 and 8 are the place to start.

The link that I placed to "Mac Pro Memory" in a previous post (above) explains.

This article discusses exactly what you want to do:
http://www.amug.org/amug-web/html/amug/reviews/articles/intel/macpro-2009/

Yes, it's true. But I think the real world effect is something like comparing a 70 degree day to a 71 degree day.
I tested every possible RAM scenario I could think of using AfterEffects and Photoshop and it made no difference at all. Only too little RAM did that and if I remember correctly that was somewhere below 12GB, probably just the original 6. I think 12 is a good base amount, maybe 16, after that it seems kind of superfluous unless you're working on extremely large files or have many, many apps open at the same time.
Maybe there are more ways now to determine if Triple Channel is really the best way to go, as in being substantially faster, but so far I've only seen it proved faster in tests like Diglloyds, not in actual applications.
It's strange, I do most anything to keep my Mac at it's fastest but after I tested this out for myself it doesn't concern me at all anymore. At least for the way I use my Mac. But if someone can show me a real world app that benefits from triple channel I will gladly reduce my RAM.