Decoding Crucial DIMM Part Numbers

Does anyone know how to decode Crucial DIMM part numbers? I currently have four sticks of CT16G4WFD8266 installed in my workstation, which were chosen because a) they are on the motherboard vendor’s QVL, and b) were available locally. These are 16GB DDR4 2666MT/s (PC4-21300) CL19 DRx8 ECC Unbuffered 288 pin DIMMs.

I now see that sticks of Crucial CT16G4DFS8266 are available locally at less than half the price I paid for the first lot. They have the exact same description attached (i.e. 16GB DDR4 2666MT/s etc.) and the Crucial website says they are 100% compatible with my motherboard.

My question is, what do the “WFD” and “DFS” represent in the part numbers? Will these modules play nicely together or is it not worth the risk?

Crucial Technology size 16GB 4bank groups, WFD and DFS should refer to die, 8Gb chips 2666MT/s.

Ever since we have standardized RAM this has been purely marketing.

Tbh, they should run together as long as your mobo can decide for some common ground in timings, I’d manually OC them anyway as those auto timings can be unstable anyway.

I decided to contact Crucial support prior to purchase, and I am glad that I did. It turns out that these two DIMMs are completely different - the first is dual rank ECC as described in the OP, while the second DIMM is single rank non-ECC. Turns out I did not read the resellers description of the second DIMM properly, and saw what I wanted to see, rather than what it actually said. Doh.

That is true for JEDEC speeds, but not for anything that is going beyond those. Considering most people buy RAM beyond JEDEC speeds and want to run it at the rated speeds too, it can get important.

Speaking from experience, running a kit (at rated speed) not on the QVL can be a pain in the ass and neither the mainboard manufacturer nor the memory manufacturer are gonna help you there. It’s more of a matter of support in the end.

the question about rated speeds comes down to few things these days on intel it’s purely how locked down is the chipset, on AMD it’s luck of draw with IMC and mobo, so nothing QVL can do for you.

… which is exactly where QVL comes into play :thinking:

Also it very much also depends on the actual chips on the sticks.

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nope it’s not, QVL is completely meaningless, the thing I’m talking about here is manufacturing variance, QVL can’t physically validate that and even if it did it can’t take into consideration your CPU etc…

I think you completely miss the point of what QVL is and/or does.

But whatever dude, you do you.

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