MP 1,1-5,1 Would this RAM work in MP 5,1?

[CBell]

Looking to upgrade the memory on my MP 5,1. I currently have 4x8GB sticks and was looking to upgrade to 16GBs because I don't really want to mess with any config files for OC. Was looking in the stickied RAM thread and found this on Amazon that looks like it matches the required specs. Just wondering if anyone's tried it out or know if it'll work before I get it.

https://www.amazon.com/gp/product/B08RMJVRH9?smid=A3LKWIQ3PBTNT2&th=1

 

[Macschrauber]

not really, 4rx4 will slow down, you need 2rx4.

Mac Pro RAM Compatibility List

Mac Pro RAM Compatibility List This thread has information on the specifications of RAM for the Mac Pro models to help you determine compatibility. This is a Wiki post so anyone with the appropriate permissions may edit it. Please help others in the community by adding compatible RAM and fixing...

forums.macrumors.com

 

[flyproductions]

not really, 4rx4 will slow down, you need 2rx4.

Yes, runs at 1066 instead of 1333...

...which in some cases is even faster than the 2R due to lower latency.

Should work perfectly fine without any real-world-noticeable difference. I am using six 32GB 4R dimms.

 

[Macschrauber]

I have seen 4r Ram dropping down to 800 Mhz when the full bank is stuffed.

 

[flyproductions]

I have seen 4r Ram dropping down to 800 Mhz when the full bank is stuffed.

Yes, they do. Populating the 4th slot is a bad idea anyway. costs about 20% of the memory performance by loosing triple channel mode. Even 2R dimms will drop to 1066MHz if four identical dimms are used.

My 32GB modules run fine @ 1066 in triple channel. Absolutely no noticeable difference to 16GB 2R sticks @ 1333.

 

[flyproductions]

not really, 4rx4 will slow down, you need 2rx4.

I did some extended testing to this particular topic, comparing 6 x 16GB 4R vs. 2R in a dual CPU 5,1.

Sent each configuration trough 10 runs of Geekbench 4.3.4. Here are the results for the memory performance:

4R

2R

As one can see, at least with this benchmark, the average overall memory performance tends to be even better with the 4R dimms. But, as one can also see, results are within a range so close, that most likely no "real world"-differences should be noticeable.

Here are two typical results.

First for the Quad Rank (4R)...

...then for the Dual Rank (2R).

As shown, not even the bandwidth, which at least should be higher for the higher frequency, shows any "real" difference.

So the "disadvantage" of using 4R vs.2R memory with the 5,1 seems to be much more of a theoretical/cosmetic issue than a real one. The effect of using 4/8 vs. 3/6 modules of the same size will always be much more significant and worse.