MP 6,1 Memory Mac Pro 6.1

[nollimac]

So, Picked up a Mac Pro 6.1 12 core and would like to max out the RAM to 128GB.

A-tech and Memory masters both have 128GB 32x4 DDR3 PC3-14900 1866mhz LRDIMM for approx. $120;
whereas OWC has 128GB 4 x 32GB PC10600 DDR3 ECC-R 1333MHz DIMMs for approx $300.

Apple specs calls for DDR3 PC3-15000 1866mhz LRDIMM, so, it appears the A-Tech and Memory masters are
closer to specs and a better offer at less than half the price of OWC's offer...is my thinking correct?

Bought it to replace a Mac Mini 2011 server that was used as a video and Photoshop editing...nothing fancy video editing.

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[tsialex]

The late-2013 Xeon memory controller is always limited to 1066MHz when you install the maximum supported RAM, 4x32GB DIMMs = 128GB.

It's a hardware design compromise, you can install more memory, but with lower memory controller frequency. So, no need at all of 1866MHz 32GB DIMMs, won't be supported at the rated frequency.

Up to 4x16GB DIMMs, 64GB, the late-2013 memory controller works at the expected 1866MHz frequency.

 

[mikas]

I don't think LR(Load Reduced)DIMMs will work in a 6,1. With 128GB RAm will run at slower speeds, I think 800MHz or 1066MHz depending on your processor. The less the cores in a CPU, the higher the memory speed, as I recall it.

 

[tsialex]

I don't think LR(Load Reduced)DIMMs will work in a 6,1.

LRDIMMs require both processor/motherboard and also firmware support for the Isolation Memory Buffer, I'm almost sure that the only Mac Pro that ever supported LRDIMMs is the 2019 Mac Pro.

With 128GB RAm will run at slower speeds, I think 800MHz or 1066MHz depending on your processor.

late-2013 Mac Pro memory controller down clocks to 1066MHz when the 32GB DIMMs are dual rank and to 800MHz for quad rank 32GB DIMMs.

The less the cores in a CPU, the higher the memory speed, as I recall it.

I never saw this info with Intel white papers, just the memory rank.

 

[nollimac]

The late-2013 Xeon memory controller is always limited to 1066MHz when you install the maximum supported RAM, 4x32GB DIMMs = 128GB.

It's a hardware design compromise, you can install more memory, but with lower memory controller frequency. So, no need at all of 1866MHz 32GB DIMMs, won't be supported at the rated frequency.

Up to 4x16GB DIMMs, 64GB, the late-2013 memory controller works at the expected 1866MHz frequency.

That's emotional disappointing...that's the first I have ever seen an Apple computer been maxed out on RAM seems to slow things down...trying to utilize old but compatible Adobe creative suite...I remembered the first time I upgraded my PowerMac 7200 to 24MB RAM cost me $1000 at OWC in 1996.

 

[tsialex]

That's emotional disappointing...that's the first I have ever seen an Apple computer been maxed out on RAM seems to slow things down

The exact same behavior also happens, with some differences, with MacPro5,1 and MacPro7,1 - seems you just never noticed. It's a Xeon memory controller design issue related to the maximum memory support (quantity of memory chips per bank and etc).

Btw, if you really need 128GB of RAM, the memory controller frequency downgrade is completely irrelevant to your workflow, you will always complete your job faster with 128GB running 1066/800MHz than with 64GB at 1866Mhz + disk swap.

 

[nollimac]

The exact same behavior also happens, with some differences, with MacPro5,1 and MacPro7,1 - seems you just never noticed. It's a Xeon memory controller design issue related to the maximum memory support (quantity of memory chips per bank and etc).

Btw, if you really need 128GB of RAM, the memory controller frequency downgrade is completely irrelevant to your workflow, you will always complete your job faster with 128GB running 1066/800MHz than with 64GB at 1866Mhz + disk swap.

Thanks for the reassurance, I had made up my mind on the 128GB RAM before I got the computer; so, I'll proceed as planned since I found a seller on eBay who have sold over 300 sets of 128GB for $185 or make an offer.

 

[adam9c1]

Who did you go with?