XMP DRAM on AM5

Simon Slays · April 28, 2023

Hi all,

I saw that there was a grey/black version and a black only version of the ram kit that I was looking for which were both rated at 6000Mhz CL30 but after further inspection I have realised that the grey/black model wasn't just a change in colour but was in fact for AMD EXPO which I guess would be better suited to AM5 than XMP. I purchased Corsair Dominator Platinum 2x16GB 6000Mhz CL30 which was £169.99 from Corsair's website and have had to wait at least a week for it so far before I can begin building my new PC as the ram was shipped from Taiwan. So I would like to know whether you think I should send that kit back and upgrade to the EXPO version which is £174.99 with the same rated speeds even though I dislike the grey colour which is why I originally chose the XMP kit.

The XMP kit that I purchased CMT32GX5M2X6000C30 has also not been tested on my motherboard (Crosshair X670E Hero) whereas the EXPO kit has CMT32GX5M2B6000Z30K

I guess what I am trying to find out is whether or not you think my XMP kit will still work perfectly fine with my 7800X3D or should I send it back and purchase the EXPO kit which I know is guaranteed to work at the rated speeds but will have to wait another week?

Thanks for reading.

RONOTHAN## · April 28, 2023

It's a little complicated.

From what I know about Corsair, the EXPO and XMP versions of that kit will almost certainly use the exact same PCB and will 100% use the same memory ICs (or at least have the same selection of ICs available for them). The only difference between them will be the SPD programming and the color of the heat spreader, that's it. Therefore, the XMP kit should be compatible with your board.

The problem comes from the fact that enabling XMP on AM5 boards is kinda sketchy, where just enabling the XMP profile of an XMP kit can cause the system to become either very unstable or just not boot at all depending on how the exact motherboard implements it. Having done a bit of memory tuning on AM5 and LGA 1700, I have my theories about why, I'll put them in a spoiler at the end if you want to hear it, though it doesn't change the fact that it is a reported phenomena. The solution seems to be to manually enter the XMP parameters and leave XMP itself disabled. Basically, if you were looking for a "one click" enable for the XMP profile, that might not work. Manually entering the timings isn't that hard, it takes me about 30 seconds to do it, there are just some people who would rather not do that under any circumstances, hence my warnings about it.

TL;DR: If you want to reliably one click enable the OC profile, send it back and get the EXPO version. If you are willing to put in 30 seconds of effort to enter the XMP profile, keep this kit when it comes in.

Anyway, my theory about why if you care:

Spoiler

Intel and AMD systems seem to calculate tRFC differently, where a setting that's relatively loose on Intel is very tight on AMD, and since the tRFC value is part of the XMP profile and just not advertised if the board doesn't take this into account it can cause the system to not boot or be very unstable. A standard tRFC value at DDR5 6000 for an Intel chip is 500-600 from what I've seen, meanwhile on AMD that value is closer to 800-1000. I haven't had any XMP kits to confirm this phenomena though, the only kits I own are Flare X5 so I'm more judging off of screen shots than anything, so take that for what you will.

Simon Slays · April 28, 2023

13 minutes ago, RONOTHAN## said:

It's a little complicated.

From what I know about Corsair, the EXPO and XMP versions of that kit will almost certainly use the exact same PCB and will 100% use the same memory ICs (or at least have the same selection of ICs available for them). The only difference between them will be the SPD programming and the color of the heat spreader, that's it. Therefore, the XMP kit should be compatible with your board.

The problem comes from the fact that enabling XMP on AM5 boards is kinda sketchy, where just enabling the XMP profile of an XMP kit can cause the system to become either very unstable or just not boot at all depending on how the exact motherboard implements it. Having done a bit of memory tuning on AM5 and LGA 1700, I have my theories about why, I'll put them in a spoiler at the end if you want to hear it, though it doesn't change the fact that it is a reported phenomena. The solution seems to be to manually enter the XMP parameters and leave XMP itself disabled. Basically, if you were looking for a "one click" enable for the XMP profile, that might not work. Manually entering the timings isn't that hard, it takes me about 30 seconds to do it, there are just some people who would rather not do that under any circumstances, hence my warnings about it.

TL;DR: If you want to reliably one click enable the OC profile, send it back and get the EXPO version. If you are willing to put in 30 seconds of effort to enter the XMP profile, keep this kit when it comes in.

Anyway, my theory about why if you care:

Hide contents

Intel and AMD systems seem to calculate tRFC differently, where a setting that's relatively loose on Intel is very tight on AMD, and since the tRFC value is part of the XMP profile and just not advertised if the board doesn't take this into account it can cause the system to not boot or be very unstable. A standard tRFC value at DDR5 6000 for an Intel chip is 500-600 from what I've seen, meanwhile on AMD that value is closer to 800-1000. I haven't had any XMP kits to confirm this phenomena though, the only kits I own are Flare X5 so I'm more judging off of screen shots than anything, so take that for what you will.

Thanks for the in depth response, I really appreciate it. I wouldn't mind manually putting in the timings as I would rather keep the black sticks since they will go better with my colour scheme which is the reason why I bought them. If I was to keep these sticks and put the same timings in that they are rated for, will I see any discernible difference in performance or stability when gaming? I would like to squeeze out as much fps as possible and if the EXPO kit will be better then I don't mind purchasing that one. Also what I meant by the XMP kit has not been tested on my Mobo is that it's not currently on the QVL list, should I be concerned about that? Thanks again.

RONOTHAN## · April 28, 2023

8 minutes ago, Simon Slays said:

If I was to keep these sticks and put the same timings in that they are rated for, will I see any discernible difference in performance or stability when gaming?

You shouldn't, practically speaking they should be identical, or at least within margin of error.

9 minutes ago, Simon Slays said:

Also what I meant by the XMP kit has not been tested on my Mobo is that it's not currently on the QVL list, should I be concerned about that?

I wouldn't. There are three main factors that matter for RAM compatibility for the QVL given a certain board, CPU, and BIOS setup: PCB, memory ICs, and rated settings. The XMP kit and EXPO kit are almost certainly running the exact same PCB, and they are both guaranteed to be some sort of Hynix memory IC (either M or A die), so those two factors are the same. The rated speed bin is so you know if a kit can actually work at a certain speed, so for AM5 if the two kits had the same PCB and ICs, but one was rated for 6000 CL30 and the other was rated for 7200 CL34, the 6000CL30 kit could be on the QVL but the 7200 kit would not. That doesn't mean that the 7200 kit wouldn't work on the board, it very much would, it just wouldn't work at the rated settings.

What likely is the reason why one is on there and the other isn't is your board vendor only tested one of them. The QVLs are only with kits they've tried, it is by no means an exhaustive list, so just because a kit isn't on the QVL doesn't mean it won't work. Plus board vendors test their QVLs with CPUs that have golden IMCs, so for the high spec kits especially just because it's on the QVL doesn't mean it would work either.