Ryzen 9 9950X with 4×32GB RAM

[csendesmark]

Hello All

Most likely I will get the Zen5 9950X, which has dual channel memory controller (wish I could afford the 7960X for the sweet 4 channel MC).
My question is:
What are the experiences with 9950X (or 9900X/7950X/7900X) with 4 installed memory modules?
Or should I go with 2×48GB over the 4×32GB?

 

[kapone32]

With all modern CPUs 2 sticks clock higher and can be more stable than using 4 sticks.

 

[A Computer Guy]

Hello All

Most likely I will get the Zen5 9950X, which has dual channel memory controller (wish I could afford the 7960X for the sweet 4 channel MC).
My question is:
What are the experiences with 9950X (or 9900X/7950X/7900X) with 4 installed memory modules?
Or should I go with 2×48GB over the 4×32GB?
View attachment 359549

My gut says go with 2×48GB but my wallet suggests 2x32GB.

 

[Zach_01]

Hello All

Most likely I will get the Zen5 9950X, which has dual channel memory controller (wish I could afford the 7960X for the sweet 4 channel MC).
My question is:
What are the experiences with 9950X (or 9900X/7950X/7900X) with 4 installed memory modules?
Or should I go with 2×48GB over the 4×32GB?
View attachment 359549

Check the "connectivity" of the CPU on the link below

https://www.amd.com/en/products/processors/desktops/ryzen/9000-series/amd-ryzen-9-9950x.html

These are the supported speeds of Zen5
2x1R DDR5-5600 MT/s
2x2R DDR5-5600 MT/s
4x1R DDR5-3600 MT/s
4x2R DDR5-3600 MT/s

...and Zen4
2x1R DDR5-5200 MT/s
2x2R DDR5-5200 MT/s
4x1R DDR5-3600 MT/s
4x2R DDR5-3600 MT/s

Anything above those speeds is not guaranteed by AMD and its considered overclock.
Better go with 2 sticks if you care about speed.
2x 32/48GB = 2x2R

R = Rank. Meaning how the sticks are populated and configured with memory chips.
Older RAM if they have chips on one side its 1R and on both sides its 2R per stick, but now there are chances that a stick can have populated 1 side and be dual ranked (high density 2R chips)

I think all 32/48GB sticks are 2R no matter the sides, but not entirely sure.
If there are 1R, then such high density chips would be very expensive.

So stick with 2 sticks if speed is important.
DDR5 6000MT/s minimum as you have very good chances to make them work at this speed.
If you want to push your luck with higher speed dont go above 6400MT/s.
But its nothing for sure that the CPU memory controller clock (UCLK) will be able to run at 3200MHz
3000MHz is pretty easy.

FCLK = Infinity Fabric Clock (CPU cores <> IO Die interconnect bus)
UCLK = CPU Unified Memory controller Clock (placed on IO Die)
MCLK = DRAM clock

Optimal speeds for 6000MT/s are
FCLK:UCLK:MCLK = 2000+:3000:3000MHz
For 6400MT/s
FCLK:UCLK:MCLK = 2133:3200:3200MHz

Number 1 rule is to keep UCLK:MCLK on equal speeds at all times
Number 2 rule is to keep FCLK as high as possible (2000+ and up to 2200MHz)
All Zen5 should be able to run FCLK 2000~2067MHz and some of them up to 2133~2200MHz (but dont count on it)

Try to find RAM specifically designed for AM5 Ryzen with EXPO profile(s)
Zen5 CPUs love high speed memory + tight(tweaked) timings (and all Ryzen love UCLK:MCLK = 1:1)

6000 CL30 or lower (tweaked)
6400 CL32 or lower (tweaked)

I think G.Skill announced recently some new Trident Z5 Royal 6000MT/s CL28 sticks
I know they have 2x48GB 6400 CL32 1.35V but kits like this are expensive (~350$, In EU maybe 390~440€ depending the exact model)

If you do go with 4 sticks (4x2R) in the end I wouldn't expect anything better than 5200MT/s or even lower.

Questions: