Question regarding early 2009 8x core RAM upgrade

[The Mad Hatter]

Like the title says, I have an Early 2009 Mac Pro w/8x 2.26 Xeon cores.

I want to upgrade the RAM to 12GBs (it currently has the stock 6GBs (6x 1GB)).

If I remember correctly, it is better to add these in sets of 3. So if I get a Crucial 12GB kit (3x 4GB), do I split them up, or put all 3 on the same quad processor (essentially giving me 15GBs if I leave both slot 4s empty)?

I would love to replace all 6 with 4GB chips but that isn't in the cards right now.

So any advice would be helpful.

 

[Butler Trumpet]

For best performance, Apple recommends you install equal-size DIMMs (all 1, 2, or 4 GB) filling the slots in the order listed here:

If you have: Two DIMMs - fill 1 and 2
If you have: Three DIMMs - fill 1, 2, and 3
If you have: Four DIMMs fill - 1, 2, and 5, 6
If you have: Six DIMMs fill - 1, 2, 3 and 5, 6, 7
If you have: Eight DIMMs fill - 1, 2, 3, 4 and 5, 6, 7, 8

Hope this helps!

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Also, if you install the RAM and the MacPro realizes that it is not installed optimally, a program called Memory Slot Utility will open and walk you through getting them installed in a more optimal way.

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One more thing...

If you want to check out Memory Slot Utility manually, you can open it here: /System/Library/Core Services (just don't mess with much else in that folder)