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octoviaa

macrumors regular
Original poster
Oct 19, 2013
172
88
Hi,

I've just installed 2x16GB RDIMM modules in slot 1 and 5, while the rest of the slot are filled with 8GB.

Currently running Mojave now, and all RAM are detected properly, as shown below:
RAM Slot allocation.png

I wonder if the slot location 1 and 5 are proper for the 16GB module, because the 'memory slot utility' seems not able to run (tried double click it in from finder but nothing happened).

Any one knows the right way to install different size of RAM module?

Resolved: https://forums.macrumors.com/threads/different-size-ram-module-2010-5-1.2173606/#post-27187357

Thank you.
 
Last edited:

DeltaMac

macrumors G5
Jul 30, 2003
13,363
4,353
Delaware
The memory slot utility should launch automatically if the memory could have a better configuration, but I am pretty sure that the different size pair (2 x 16 GB) should be in slots 1 and 2, not 1 and 5
 

expede

macrumors regular
Jan 15, 2018
236
66
Sweden
Ok, here is the manual.

/Per
 

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octoviaa

macrumors regular
Original poster
Oct 19, 2013
172
88
Ok, here is the manual.

/Per
Hi expede,

I've got the manual however couldn't really tell where to put my 16GB vs 8GB.
There is no word like "put your higher capacity RAM in the lowest number slot" so I still have the question.

The only thing it mentioned regarding the optimal location slot location is 'Memory Slot Utility' will pop up a warning if my RAM placement is no optimised. However I can't run the utility to make sure my RAM placement are correct.

Thank
[doublepost=1552787279][/doublepost]
The memory slot utility should launch automatically if the memory could have a better configuration, but I am pretty sure that the different size pair (2 x 16 GB) should be in slots 1 and 2, not 1 and 5

To my knowledge we need to balance the RAM size for the dual CPU, hence I put in slot 1 & 5 instead of 1 & 2 as slot 2 belong to the same CPU as slot 1, while slot 5 is for the other one, so with 1 & 5, I balance the total RAM size for each CPU (40GB for each).
Unless my understanding is in-correct I did assume 1-4 are for CPU A while 5 - 8 are for CPU B, please kindly correct me if I'm wrong
 
Last edited:

tsialex

macrumors G5
Jun 13, 2016
12,707
12,965
To my knowledge we need to balance the RAM size for the dual CPU, hence I put in slot 1 & 5 instead of 1 & 2 as slot 2 belong to the same CPU as slot 1, while slot 5 is for the other one, so with 1 & 5, I balance the total RAM size for each CPU (40GB for each).
Yes, it's correct. You have to do exactly as you are doing, you have to split equally the RAM with each controller.
 
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DeltaMac

macrumors G5
Jul 30, 2003
13,363
4,353
Delaware
OK, but why would Apple's service manual say "If you install different-size DIMMs in single-processor or dual-processor Mac Pro (Mid 2010/ Mid 2012), follow the order in the tables above" That table would seem to say that one (different) pair goes in slot 1 and 2.
But, if wrong, the memory slot utility should then appear to give another take on that, so it would seem.
So, then slots 1 & 5 should be good (because the memory slot utility doesn't launch)

I will defer to @tsialex, you have more experience on the MP than I do.
BUT, what happens if you have a full load of RAM, and decide to move the one large pair to slot 1 and 2, leaving smaller pairs on all other slots. Do you expect the memory slot utility to pop up? and the reason it does NOT appear for the OP is that the memory configuration is the optimum (and correct) using slots 1 and 5?
 

tsialex

macrumors G5
Jun 13, 2016
12,707
12,965
OK, but why would Apple's service manual say "If you install different-size DIMMs in single-processor or dual-processor Mac Pro (Mid 2010/ Mid 2012), follow the order in the tables above" That table would seem to say that one (different) pair goes in slot 1 and 2.
But, if wrong, the memory slot utility should then appear to give another take on that, so it would seem.
So, then slots 1 & 5 should be good (because the memory slot utility doesn't launch)

I will defer to @tsialex, you have more experience on the MP than I do.
BUT, what happens if you have a full load of RAM, and decide to move the one large pair to slot 1 and 2, leaving smaller pairs on all other slots. Do you expect the memory slot utility to pop up? and the reason it does NOT appear for the OP is that the memory configuration is the optimum (and correct) using slots 1 and 5?
You have to balance the RAM with the two controllers, or you will have frequent NUMA penalties with RAM access.

Memory Utility still works? I don't remember it working since at least Sierra, but maybe it's because I try to organise the RAM correctly and it was never needed, but I really don't know if it still works.
 

octoviaa

macrumors regular
Original poster
Oct 19, 2013
172
88
You have to balance the RAM with the two controllers, or you will have frequent NUMA penalties with RAM access.

Memory Utility still works? I don't remember it working since at least Sierra, but maybe it's because I try to organise the RAM correctly and it was never needed, but I really don't know if it still works.

Thanks Alex for the confirmation.

The Memory Slot Utility doesn't seem to work anymore, even when I use sudo (sudo open "Memory Slot Utility") nothing comes up.

Thank you @DeltaMac and @expede too.
 

Macschrauber

macrumors 68030
Dec 27, 2015
2,688
1,328
Germany
Once memory Utility popped up when starting a 4.1 Dual with 10.7 telling me to organize 4x8GB and 4x4 differently. Didnt popped up in 10.13 nor 10.14
 
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