MP 7,1 RAM on MP7,1: Does different sized sticks or using more than 6 slots reduce speed?

[Korican100]

I have been asking here and there on different threads, and I'm still not sure. Forgive my lack of knowledge on this.

i have a 16core machine, with 48gb RAM right now in my 7,1. (6 slots have a 8GB stick.)
I plan on adding some 32GB sticks (matching specs and all that). So here are my concerns:

1. If I keep my 48gb, and add 2 x 32GB sticks to slot 7 and 8. What kind of reduced speeds can I expect now that ive surpassed 6 channels?
2. If I take out 2 x GB Sticks from slots 5 and 6, and replace them with 2 x 32GB sticks, im still leveraging 6 channels, but does the different sizes cause any performance issues?

What would be the best solution to my situation of wanting to increase RAM size (with 2 x 32GB sticks, while keeping my Apple sticks, and maintaining high performance?

 

[JoeMaj]

This article/video should help:

How to upgrade Mac Pro RAM and save lots of money [Video] - 9to5Mac

This tutorial shows you How to upgrade Mac Pro RAM and save lots of money that can be used to upgrade other components in your Mac.

9to5mac.com

 

[majus]

... and add 2 x 32GB sticks to slot 7 and 8.

Please read the document at this link before you install any additional memory. It will answer all of your questions -- except about performance.

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

 

[bxs]

Your 48 GB (6 x 8GB DIMMs) are likely to occupy slots 1, 3, 5, 8, 10 and 12. This utilizes memory channels 1, 2, 3.

Now to add 64 GB (2 x 32GB DIMMs), then place them in slots 6 and 7 and this utilizes memory channel 4.

You end up using 8 slots with 4 slots empty. These four slots can be used later using slots 4 and 9 for memory channel 5 and slots 2 and 11 for memory channel 6.

All of this can been gleaned from the Ref given by member majus posted.

 

[Korican100]

Thanks guys. I saw the document of the order of slots to occupy. I should have clarified that in my post.

I’m just really concerned about performance hits for bullets 1 and 2 in my original post.

 

[bxs]

Thanks guys. I saw the document of the order of slots to occupy. I should have clarified that in my post.

I’m just really concerned about performance hits for bullets 1 and 2 in my original post.

According to Apple, "Use the same size memory modules across all slots to maximize performance". Thus, anything different from this presumably will lower the memory performance. IMO, for most of us this will be negligible or unnoticeable (my speculation).

 

[bsbeamer]

If you’re worried about performance, make sure EVERYTHING matches - size, speed, and all detailed specs. Any mismatch can create issues with performance. WHEN you might notice that performance hit may be more of a concern.

This machine is $6K+ and most of the configs I’m seeing from people here have well exceed that. Don’t cheap out on your RAM after investing this much into squeezing out GPU performance. You’ll notice RAM performance hit or conflict issues before anything else, sometimes even before SSD (once past ~400MB/s speed range).

 

[Korican100]

If you’re worried about performance, make sure EVERYTHING matches - size, speed, and all detailed specs. Any mismatch can create issues with performance. WHEN you might notice that performance hit may be more of a concern.

This machine is $6K+ and most of the configs I’m seeing from people here have well exceed that. Don’t cheap out on your RAM after investing this much into squeezing out GPU performance. You’ll notice RAM performance hit or conflict issues before anything else, sometimes even before SSD (once past ~400MB/s speed range).

im not necessarily cheaping out i'd say. I want to keep my 48gb from apple and then add additional sticks. My concern is since the existing sticks are 8GB sticks, and I want to add sticks that are 32gb sticks. Also, using anything beyond a 6 or 12 channel setup would also cause a hit.

I would assume if there is a performance hit, it would be negligible from a real world perspective.

Just want to know if anyone can shed light on how much of a hit it would be.

 

[bsbeamer]

You’re looking for metrics and stats that require hands on with this specific machine and this specific RAM spec with this specific processor. Too many variables to try to use any other CPU/config as guidance.

Personally think you’re better off with 4x32GB or 6x32GB than trying to mix any 32GB with the 8GBs. Mixing is nothing more than trying to save a few bucks - machine fully works with 32GB modules, you “just” need to buy them. If you’re adding multiple 8GB sticks to existing 8GB sticks, that’s a different story.

Good luck.

 

[OkiRun]

Thanks guys. I saw the document of the order of slots to occupy. I should have clarified that in my post.

I’m just really concerned about performance hits for bullets 1 and 2 in my original post.

I posted this in another thread you commented in ~
I decided against ordering the 48b kit and will order the 32Gb kit. I just purchased 6 Crucial 32Gb RAM chips in order to keep everything standard. The cost of these 6 sticks is 2K less than the Apple configuration cost.
Not getting Afterburner at this time which adds another 2K to go toward the XDR Monitor; will get the Apple stand. But please, no boos.

 

[MacUser2525]

im not necessarily cheaping out i'd say. I want to keep my 48gb from apple and then add additional sticks. My concern is since the existing sticks are 8GB sticks, and I want to add sticks that are 32gb sticks. Also, using anything beyond a 6 or 12 channel setup would also cause a hit.

I would assume if there is a performance hit, it would be negligible from a real world perspective.

Just want to know if anyone can shed light on how much of a hit it would be.

It is a couple of percent on the benchmarks if you have an unbalanced ram setup like you propose. I doubt in the real world you notice much difference if you actually need all that ram. I would think that the getting close to that extra 64gb with (6x8gb) filling the other six channel slots is the best option really. The ram runs as designed for best speed, unless you absolutely need the extra 16gb....

 

[Korican100]

It is a couple of percent on the benchmarks if you have an unbalanced ram setup like you propose. I doubt in the real world you notice much difference if you actually need all that ram. I would think that the getting close to that extra 64gb with (6x8gb) filling the other six channel slots is the best option really. The ram runs as designed for best speed, unless you absolutely need the extra 16gb....

i was thinking about that as well. i dont see myself hitting that 96gb limit anytime soon.
Now its just a concern of using Apple's 8GB sticks with non-apple 8gb sticks

 

[MacUser2525]

i was thinking about that as well. i dont see myself hitting that 96gb limit anytime soon.
Now its just a concern of using Apple's 8GB sticks with non-apple 8gb sticks

They are not Apple sticks they are standard server ram sticks, look at the label buy the same brand, part number and you have no worries. You should have none if another brand same type of ram with the identical timing, latency, all them fun things. But best to stick to the identical as it will certainly just work properly no fuss.