Ram slot configuration

IanK MacPro

macrumors member
Original poster
Jul 6, 2018
61
37
Buckinghamshire, UK
Hi Everyone, I'm just about to upgrade the ram on my 3x MacPro 4.1>5.1's, all 12-core 3.46.

2 of the machines are running dual 1080ti's for redshift rendering and could do with a bit more ram.

They all currently have 32GB (8x 4gb) and I'm about to purchase an extra 4x 16gb for each machine which will leave me with the potential to upgrade to more if needed in the future.

With 4x 16gb installed, will I be ok filling the remaining empty slots with 4x 4gb or will there be any issues?

Also if I do go this route, what would be the best slot configuration for a mix of 4x 16gb & 4x 4gb?

Any help greatly appreciated!
 
Last edited:

expede

macrumors regular
Jan 15, 2018
203
54
Sweden

This means that you first you put the 16GB in slot 1,2,5,6 and the rest 4GB in the rest
/Per
 

h9826790

macrumors G5
Apr 3, 2014
14,108
6,733
Hong Kong
Don’t worry about the difference in capacity. If they are not in optimum config, the OS will tell you once boot to desktop, just copy the recommended config, then shut down, and re-arrange your DIMM.

However, you have to worry more about if your current DIMM are RDIMM. Your 16GB DIMM should be RDIMM, if your current 4GB DIMM are UDIMM, then they cannot be used together.
 
Last edited:

tsialex

macrumors 604
Jun 13, 2016
7,613
8,347
Brazil
The best way is to put the same amount of RAM to each processor, so one don't need to use NUMA so much. The best way is to put 2 16GB DIMMs and 2 4GB DIMMs for each processor.
 
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IanK MacPro

macrumors member
Original poster
Jul 6, 2018
61
37
Buckinghamshire, UK
Received the 16gb DIMMS today, all works fine in the following configuration:

Slot1: 16gb Slot2: 16gb
Slot3: 4gb Slot4: 4gb

Slot5: 16gb Slot6: 16gb
Slot7: 4gb Slot8: 4gb

Total: 80Gb

My old 4gb DIMMS all had heat spreaders on them, is it worth transferring these over to the new 16Gb modules?

memory.jpg
 

tsialex

macrumors 604
Jun 13, 2016
7,613
8,347
Brazil
Received the 16gb DIMMS today, all works fine in the following configuration:

Slot1: 16gb Slot2: 16gb
Slot3: 4gb Slot4: 4gb

Slot5: 16gb Slot6: 16gb
Slot7: 4gb Slot8: 4gb

Total: 80Gb

My old 4gb DIMMS all had heat spreaders on them, is it worth transferring these over to the new 16Gb modules?

View attachment 795779
Check your RAM temperatures with iStat or another app, if the new ones are hotter that the old ones, do the heat spreader swap.

Test your new memory a lot before doing that, you probably will loose your warranty. I usually only do the heat spreader install after the warranty/return window expires.
 

IanK MacPro

macrumors member
Original poster
Jul 6, 2018
61
37
Buckinghamshire, UK
Check your RAM temperatures with iStat or another app, if the new ones are hotter that the old ones, do the heat spreader swap.

Test your new memory a lot before doing that, you probably will loose your warranty. I usually only do the heat spreader install after the warranty/return window expires.
Great, will do. Thanks for the advice
 

Zeke D

macrumors 65816
Nov 18, 2011
1,010
160
Arizona
Only slightly off topic.
I my 2010, I had followed the manual with four identical 4GB ECC dimms, and placed them in slots 1,2 & 5,6. I tossed in a Lion install, and the memory slot utility popped up and suggested that I put them in slots 2,3 & 6,7.

I moved the DIMMs, and saw no performance decrease running Sierra. Any ideas why the memory slot utility suggested a configuration contrary to the manual?
 

h9826790

macrumors G5
Apr 3, 2014
14,108
6,733
Hong Kong
Only slightly off topic.
I my 2010, I had followed the manual with four identical 4GB ECC dimms, and placed them in slots 1,2 & 5,6. I tossed in a Lion install, and the memory slot utility popped up and suggested that I put them in slots 2,3 & 6,7.

I moved the DIMMs, and saw no performance decrease running Sierra. Any ideas why the memory slot utility suggested a configuration contrary to the manual?
No idea, but that won't make any difference anyway, each DIMM still has their own channel.

IMO, just follow the memory slot utility's suggestion can't go wrong. It's definitely more update than the original manual, and it's directly from Apple.
 
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