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Thread: Can you mix 8gb sticks in Nehalem machines?

  1. #1
    Join Date
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    Default Can you mix 8gb sticks in Nehalem machines?

    I first ran into some question about this shopping for RAM on Crucial or OWC, can't recall which.

    My interest is in getting the absolute MAX bang for whatever buck, and I've only recently been introduced to the idea of triple-channel setups and the possibility that the right setup can trump total gigs.

    So if I were to use three 8gb sticks in slots 1-2-3 and three 4gb sticks in slots 5-6-7, would that work? What about three-channel 123 then one 8gb in slot 5?

    Where am I better off going without the extra ram if I can't configure it the best way?

  2. #2
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    Interesting,

    I have never tried 3 + 3 module setup. 4 + 4, 6 + 2, and 8 total, never 3's. I don't know how the effect on performance would be.

    Rick
    molṑn labe'
    "I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin

  3. #3
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    Quote Originally Posted by ricks View Post
    Interesting,

    I have never tried 3 + 3 module setup. 4 + 4, 6 + 2, and 8 total, never 3's. I don't know how the effect on performance would be.

    Rick
    Well the 3+3 is supposed to be the ideal configuration, it's called triple-channel and what I read is that it's better to leave those extra slots open, that filling them actually impedes performance.

    I'm just confused about the big sticks, 8 and 16 gig.

  4. #4
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    I recall reading that......and thinking: Weird. Just for that one model as I recall, must be the memory controller.

    Here's the install guide. Be sure this is right for your model.

    If you fill all the slots.....I'm not sure it really matters. Have read that even not optimized, you only lose about 1-2% of performance.
    Last edited by unclemac; 02-16-2012 at 08:45 AM.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  5. #5
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    ANother interesting factor, when we test, Apple's Memory Utility forces some sometimes strange setups. Last time I tested I had 6 x 8 GB modules and 4 x 2 GB modules in hand. This was in a more recent model MacPro 5,1. I installed the 8 GBers in 123567 and a couple of the 2 GB modules in the remaining 48 slots. No problem. Then, when I pulled the 8's to ship, I put the 2's back in 1,2,5,6 like it shipped from the factory. Memory Utility first made me move to 2356, then 2367 before it allowed that it was correct. This leaves me wondering if we can predict the criteria followed by Memory Utility. My results have shown that the utility may not follow its own rules twice.
    molṑn labe'
    "I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin

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