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Which of these two memories is better / faster under heavy loads?

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Hi everyone,

I'm setting up a new system with MOBO ASUS Pro WS X299 SAGE II (https://www.asus.com/Commercial-Servers-Workstations/Pro-WS-X299-SAGE-II/) and bought the following Corsair Vengeance memory already a while ago (it was a really good special in amazon.co.uk): https://www.corsair.com/uk/en/Categories/Products/Memory/VENGEANCE-LPX/p/CMK32GX4M4K4133C19   judging by the memory base speed I'd get effectively without OC 4133Mhz read-write speeds using these modules. But since I have 8 RAM module slots available and would like to be on the 256GB side I was re-thinking which RAM I'd use.

Then I went to check for the fastest / best alternative that Corsair could offer for my new system. I found in top of the list (searching by compatibility) the Dominator Platinum RGB 128GB which with two sets of 4 modules would allow me to reach my goal of 256GB RAM https://www.corsair.com/eu/en/Categories/Products/Memory/DOMINATOR-PLATINUM-RGB/p/CMT128GX4M4E3200C16

It would seem that this is the best RAM Corsair could offer for my system and as I understand Dominator is the top line from Corsair but how come it is only 3200Mhz and the Vengeance I already got is 4133Mhz. I am confused, will the Dominator version be nevertheless faster despite the lower base speeds specs of 3200Mhz???


Many TIA,

Best regards,


Edited by bravegag
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Because no one can possibly run 256GB of RAM at 4133 MHz on a X299 or any other system on DDR4.  I don't know if you really need 256 vs 128GB, but presumably your choice reflects the need for this system to run professional workloads where an error 46 minutes into a batch is going to be major issue.  Splicing together 4 separate kits is a recipe for disaster and they are sold as a matched set for a reason.  While this may be worth a gamble for someone playing games and listening to music, it is poor odds for those with memory intensive tasks.  


The Memory Finder may not be exactly up to date.  Try a manual search for DDR4 and 256GB kits.  That should give you 8 results in that size.  I would avoid the Vengeance Pro RGB RAM for your presumed intended use.  It runs hotter than the Dominator, LPX, and Vengeance RT heatsinks and with 2 banks of 4 and long runs, this may be relevant.  


When Asus lists "8 x DIMM, Max. 256GB, DDR4 4266(O.C.)/4200(O.C.)/4133(O.C.)/4000(O.C.)/3600(O.C.)/2933/2666/2400 MHz Non-ECC, Un-buffered Memory", they are not stating you can run 256GB at 4266.  They are listing the physical limitations of the board as separate categories.  It can hold 8 modules of 16GB density.  The BIOS will allow you to get frequencies up to 4266.  That does not mean you can run them.   I can't judge the stability of 3600 vs 3200 on your MB/CPU combination, but non-existence of anything past 3600 suggests that is the maximum viable frequency at that volume.  You may want to google around for other X299 WS owners to see where they are for this volume of RAM.

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Posted (edited)

Thanks for your answer.

Are you saying that getting 2x 128GB Corsair Dominator here: https://www.corsair.com/eu/en/Categories/Products/Memory/DOMINATOR-PLATINUM-RGB/p/CMT128GX4M4E3200C16

Is not the same as 1x of 256 Corsair Dominator here? https://www.corsair.com/ww/en/Categories/Products/Memory/DOMINATOR-PLATINUM-RGB/p/CMT256GX4M8E3200C16

These two sets look identical to me, only difference is the number of RAM modules. I never implied that I was going to mix in different RAM types.

Your comments left me thinking but indeed in my case I need as much RAM as possible. I will run Windows 11 Pro with WSL Ubuntu, where I will run heavy ML workloads: massive concurrent scenario testing with parallel ML model calibration. e.g. sklearn, TensorFlow, etc. I need intra and inter-parallelism so SIMD with CUDA, and inter-parallelism to parallelize data processing pipelines e.g. Spark. I have the Intel i9-10980xe (18 cores) and the Asus RTX 3090. So yes I want the fastest memory for capacity with the two choices above and to get 256GB I could get 2x 128GB or 1x set of 256GB. I will then sell my unused boxed Vengeance 4133Mhz 🙂



Edited by bravegag
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RAM is a sensitive physical material and differences between modules cause a problem. Not every kit of Brand X, model abc123 is going to be the same. They may have come from completely different semi-conductor IC manufacturers and/or different production runs from different raw materials. Most manufacturers note this in some way with their version numbers, but those are not an advertised or guaranteed part of the product purchase. Corsair uses version numbers ranging from 3.xx to 8.xx where the first number denotes different IC manufacturers and the post decimal is the batch or production run. 

If you are running two RAM modules on a dual channel board, you have a lot more wiggle room in regards to differences. As you move toward the extremes — high frequency, high volume, or high density — your wiggle room disappears. At 128 or 256GB I would be careful. I do think on a dual bank, quad channel board like a X299 WS board you may be able to use two 128GB kits with the same version number, but I would only do this if there is a meaningful economic advantage to buying them as 128gb kits. This is not a shortcut to higher frequency and 2x128GB kits with XMP 3866 likely can’t run that when combined. However, as you shop around I think you’ll see most 128 and 256 kits are fairly aligned in term of frequency and timing, so this will mostly be a matter of price. You are also more likely to get the same version number on two 128Gb kits because the market here is smaller and not as transitory as the 2x8 and 2x16 high volume products that seem to change every few months. 

Edited by c-attack
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Hi c-attack,

Thanks a lot for your detailed feedback and help, this is an eye opener for me. I thought that if RAM models matched perfectly e.g. as you mention abc123, I could combine those or even buy one set today, wait for the price to decrease in the future and buy a second set, but this seems not to be the case. Actually I understand now I got myself into that issue with my current built where I initially bought 16GB DDR3 of model CMT16GX3M4X2133C9, then after 5 years got a second CMT16GX3M4X2133C9 and had to fight with the BIOS to get the memories to work without crashing, I even had to lower the OC speeds to the minimum, I had it working at the end but didn't understand why 🙂

My current (very old) build:


- Intel Core i7 4960x

- 2x CMT16GX3M4X2133C9

- ASUS Strix 2080ti

I only buy Intel and nVidia because I work with Intel developer HPC toolkits such as Intel Compilers (C++, fortran), Intel Math Kernel library (MKL) linear Algebra optimized kernels for HPC/ML. I code CUDA as well again to speed up ML algorithms and auto-speed-up frameworks such as numpy, tensorflow, etc. For example, with the current build I have if I run a simple feature selection in sklearn, and a reasonable small data set, I never get an answer back after hours running 😞

Concretely now, I have the problem that here in Switzerland there isn't availability for the 256GB set but only the 128GB is available, so I could not get the 256GB even if I wanted to, and yes the 256GB would be perfect because is even cheaper than 2x 128GB.

If I understood correctly from what you said, then 3200MHz is the best I can get for a capacity of 256GB RAM

Best! Giovanni

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There are some 3600 MHz 128 and 256 GB kits listed. Whether or not that is a viable speed for x299 at that capacity is another matter.  How much time saved per run with +400 MHz is also something I can answer, so it’s hard to weigh the extra cost. Given the already hefty price, it seems like it would be worthwhile to go for 3600 if available. You can always drop a 3600 kit down to 3200, but going up may not be possible. 

Availability is always an issue with these large kits. There were never as many to begin with, but that also means you won’t see the 9 different versions of Dominator Platinum 3200c16 256GB like you might with a new 2x16 DDR5 kit.  However, I am having a hard time finding any meaningful discussion about 128 vs 256 capacity and/or limitations for this board.  I can find the questions asked, but no real answers.  Additionally it looks like the board didn’t support 32GB modules at launch (or more likely we didn’t have them) so the original max capacity was 8 x 16GB = 128.  


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