AMD 7950x and 128GB DDR5 RAM

[0wN3r]

Hi everyone!

 

I'm currently upgrading my setup and adding machine which will be primarily used as a server hosting my development environment (developing software, running remote IDEs and hosting databases). Justification of the specs aside, I would love to hear your thoughts on the current state of affairs with DDR5 on AM5 platform.

 

As it stands, it seems that very few vendors produce DDR5 128GB kits dedicated for EXPO, but some can be found. The AMD's limitations for 7950x state the max memory speed constraints as follows:

Max Memory Speed

2x1R - DDR5-5200

2x2R - DDR5-5200

4x1R - DDR5-3600

4x2R - DDR5-3600

 

This suggests that in the best case scenario, I will be able to run a kit of 4x32GB sticks at 3600MT/s.

 

My questions to you are:

1. How do these speeds compare to the kits sold by vendors like Corsair or GSkill who sell them with EXPO profiles clocked as high as 6400MT/s with latencies as low as 28CL? Are these speeds officially supported for the DIMMs provided, but depend on whether the CPU can actually run them (silicon-lottery)? Does that mean that AMD are essentially just covering themselves by saying the official supported speeds are 5200 and 3600MT/s respectively (in the worst case scenario for the CPU)?

2. I'm assuming that purchasing a 2x32GB 6000MT/s is the safest bet compatibility wise, given how fussy the memory controllers are with 4DIMMs (and bearing in mind QVLs rarely testing 4x8GB RAM which I'm guessing is 1R or 2R/DIMM); does that ring true?

3. If I bought 2 separate kits of 2x32GB 6000MT/s RAM, could I run them together at 3600MT/s and perhaps more if overclocked (with the risk of upsetting memory controller)?

4. Are there any news on how this situation might change in the future? Is this issue more dependent on hardware itself, or can we expect BIOS updates / new RAM kits that support 128GB (both 4x32 or 2x64) to come out?

 

Thanks for any help and insights! 

[igormp]

7 minutes ago, 0wN3r said:

Are these speeds officially supported for the DIMMs provided, but depend on whether the CPU can actually run them (silicon-lottery)? Does that mean that AMD are essentially just covering themselves by saying the official supported speeds are 5200 and 3600MT/s respectively (in the worst case scenario for the CPU)?

Yes and yes.

7 minutes ago, 0wN3r said:

2. I'm assuming that purchasing a 2x32GB 6000MT/s is the safest bet compatibility wise, given how fussy the memory controllers are with 4DIMMs (and bearing in mind QVLs rarely testing 4x8GB RAM which I'm guessing is 1R or 2R/DIMM); does that ring true?

Yes.

7 minutes ago, 0wN3r said:

3. If I bought 2 separate kits of 2x32GB 6000MT/s RAM, could I run them together at 3600MT/s and perhaps more if overclocked (with the risk of upsetting memory controller)?

Yes, you may want to take a look at the neighbor forum, there's a thread specific to running 128gb on am5:

https://forum.level1techs.com/t/7950x-i-want-4x32gb-unless-it-sucks-does-it-suck/189825

 

Seems like people managed 4400~4800MHz manually without many issues.

 

9 minutes ago, 0wN3r said:

4. Are there any news on how this situation might change in the future? Is this issue more dependent on hardware itself, or can we expect BIOS updates / new RAM kits that support 128GB (both 4x32 or 2x64) to come out?

It may be a bit better, but won't change the fact that you'll have 4 DIMMs stressing out the controller. The best option would be to have 2x64gb as you mentioned, but there's no sign of those as of today for the consumer market.

[ewitte]

I have no experience with 7000 series but 1000,2000, 3000 series I couldn't get it to work at decent speeds with 4 ram chips.  It ran just fine full 3600Mhz with my 5900x though.  I'm planning on doing a 2x32GB DDR5 6000 kit when I eventually upgrade (Zen5 likely).

[igormp]

16 minutes ago, ewitte said:

I have no experience with 7000 series but 1000,2000, 3000 series I couldn't get it to work at decent speeds with 4 ram chips.  It ran just fine full 3600Mhz with my 5900x though.  I'm planning on doing a 2x32GB DDR5 6000 kit when I eventually upgrade (Zen5 likely).

I had a 3700x that ran fine with 2x32gb, and now have a 5950x with 4x32gb @3200mhz running smoothly. A friend of mine also has 2x32gb but with a 1600af running without problems too.

Sure, at those speeds it's pretty much a given, but still...

 

I have no interest in the current DDR5 gen since there's no indication of support for more than 128gb for mainstream platforms (which I currently have already), and I'm not willing to spend way too much money on a HEDT platform.