MP 7,1 7.1 and 2x 64GB DIMMs

[pierre1610]

As titles, I want 128GB ram.
2x 64GB DIMMs will mean they are LR-DIMMs. OWC tell me it will run (without standard memory as that is rDIMM)
My question is will it run slowly seeing as it’s quad channel memory.

It will be on a 12 core so the faster ram

 

[AidenShaw]

As titles, I want 128GB ram.
2x 64GB DIMMs will mean they are LR-DIMMs. OWC tell me it will run (without standard memory as that is rDIMM)
My question is will it run slowly seeing as it’s quad channel memory.

It will be on a 12 core so the faster ram

Actually, the 7,1 is hex-channel. Apple puts quad DIMMs in a hex motherboard in the standard configs.

In real applications, the large caches often hide any differences in RAM configurations.

There's a thread at https://forums.macrumors.com/thread...bservations-with-various-mem-configs.1704700/ analyzing the performance of an MP6,1 with one, two, three, and four DIMMs. (6,1 is quad channel)

For most tests, the number of DIMMs made little difference - only a couple of "bandwidth virus" tests showed significant loss due to not fully populating the channels.

 

[pierre1610]

Has anyone tried this with a 7.1?

 

[Z28McCrory]

I gained around 1800 points of GB5.1 multi core score (14,000 to 15,800) on my 16 core when I went from 4 channel (4x8GB) to 6 channel (6x32GB). Seeing that, 2 channel would have to show a performance drop.

 

[pierre1610]

I gained around 1800 points of GB5.1 multi core score (14,000 to 15,800) on my 16 core when I went from 4 channel (4x8GB) to 6 channel (6x32GB). Seeing that, 2 channel would have to show a performance drop.

you ditched the original 32gb (4x8gb)?

 

[Z28McCrory]

you ditched the original 32gb (4x8gb)?

Yes. I wanted 6 matching DIMMs. Mixing sizing like that would hurt more than it helps.

 

[jasonmvp]

Yes. I wanted 6 matching DIMMs. Mixing sizing like that would hurt more than it helps.

This is a bit of a stretch. The 6 x <identical size> DIMMs will help in overall benchmark performance, yes. But if your workload needs the RAM and it's easier to just add two more DIMMs, then that's a win.

 

[Z28McCrory]

This is a bit of a stretch. The 6 x <identical size> DIMMs will help in overall benchmark performance, yes. But if your workload needs the RAM and it's easier to just add two more DIMMs, then that's a win.

Having 192 GB of perfectly matched DIMMs will always outperform 224 GB of mismatched DIMMs, unless you’re currently using more that 192 GB of RAM.

In my case, this is 99.999% of the time. If I needed more than 192GB I’d do it by jumping to 384GB.

 

[jasonmvp]

Having 192 GB of perfectly matched DIMMs will always outperform 224 GB of mismatched DIMMs, unless you’re currently using more that 192 GB of RAM.

That was my point. The difference in performance you're going to see in almost any application you're running will basically be nil. It's only in the benchmarks that you'll see much of a difference. And again: having more RAM if you need it will be far more beneficial than having match RAM.

 

[erroneous]

As titles, I want 128GB ram.
2x 64GB DIMMs will mean they are LR-DIMMs. OWC tell me it will run (without standard memory as that is rDIMM)
My question is will it run slowly seeing as it’s quad channel memory.

It will be on a 12 core so the faster ram

The Apple support document for the new Mac Pro states that configurations with 1/2/3 dimms should only be used for “diagnostic reasons.”

Install and replace memory in your Mac Pro (2019) - Apple Support

Learn how to remove and install memory in your Mac Pro.

support.apple.com

 

[OkiRun]

One question I do have about the 7.1 and RAM configuration...

Should not the 8Gb sticks be in Channel 1 for an 8 chip configuration?

 

[erroneous]

One question I do have about the 7.1 and RAM configuration...

Should not the 8Gb sticks be in Channel 1 for an 8 chip configuration?

I've seen a few people in threads here being advised by Apple support that the "smallest modules first" direction is the wrong way around, or doesn't mean what we think it does.

I had a set of green ticks from the memory advisor when I tried 10 sticks (4x8, 6x32) with sticks in similar "wrong" positions as in your screenshot.

https://forums.macrumors.com/attachments/screenshot-2020-01-05-at-13-21-30-png.886826/

 

[OkiRun]

I've seen a few people in threads here being advised by Apple support that the "smallest modules first" direction is the wrong way around, or doesn't mean what we think it does.

I had a set of green ticks from the memory advisor when I tried 10 sticks (4x8, 6x32) with sticks in similar "wrong" positions as in your screenshot.

https://forums.macrumors.com/attachments/screenshot-2020-01-05-at-13-21-30-png.886826/

Thanks. It can take hours searching for a kernel of information like this.

 

[bxs]

• Populating two slots with 64GB DIMMs can be done, if done correctly.
• The DIMMs can be configured in two different ways; one will be balanced, but the other will be unbalanced.
• The balanced configuration using two identical size DIMMs will give you around 35% of the maximum memory bandwidth.
• The unbalanced configuration using two identical size DIMMs will give you around 34% of the maximum memory bandwidth.
• The STREAM benchmark for estimating memory bandwidth is used to determine the above.
• The maximum memory bandwidth (i.e., 100%) can only be achieved by populating ALL 12 DIMM slots.

 

[RyanFlynn]

I gained around 1800 points of GB5.1 multi core score (14,000 to 15,800) on my 16 core when I went from 4 channel (4x8GB) to 6 channel (6x32GB). Seeing that, 2 channel would have to show a performance drop.

I had the exact experience

 

[Parzival]

The maximum memory bandwidth (i.e., 100%) can only be achieved by populating ALL 12 DIMM slots

Is there an official document somewhere that mentions this?

 

[bxs]

Is there an official document somewhere that mentions this?

Read this -> https://lenovopress.com/lp0742.pdf It's a good read and comprehensive....

Example of its conclusions... see attached images.