RAM Latency: CL40 RAM Runs at CL40, not CL42!

I thought I should point this out in case anyone is wondering about this. I ordered this RAM for my batch 17 FW 16 (Ryzen 7 7840 HS). I was expected it to default to CL42, but when I put together my laptop today, both CPU-Z and HWInfo64 confirmed that it was running at 40-40-40-90! That was a pleasant surprise!

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Makes perfect sense CL40 would run at CL40.

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Yes, but I was expecting it to default to CL42, because until then, I was not aware that the framework supports CL40.

There isn’t much info for this online, so I mainly put this out here for people like me who are wondering, but can’t find any info.

Why did you expect CL42?

The DDR5 spec for 5600 specifies that the only standardized CL timings allowed are CL40, CL46, and CL50. Framework does not support non-standard timings so CL42 isn’t unsupported.

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Framework supports jdec timings, 5600 cl40 is one of them.

Don’t think I have ever seen any 5600 cl42 jdec sticks before, it seems to be either cl40 or cl46.

Correct, the JEDEC spec lists 4 timing classes for JEDEC compliant 5600 MT/s modules.

Those 4 timings classes are:

  • 5600AN: 40-40-40
  • 5600B: 46-45-45
  • 5600BN: 46-46-46
  • 5600C: 50-49-49

Most 5600 MT/s kits (including Framework branded modules) are 5600B, however there are also some 5600AN kits (such as the G.Skill kit that OP and I both have as well as a Kingston kit) and I think some 5600BN kits. I haven’t seen any 5600C kits.

The JEDEC spec follows a pretty consistent pattern for the timing classes. “A” means the lowest timing that has a latency greater than 14 ns, “B” means the lowest timing that has a latency greater than 16 ns, “C” means the lowest timing that has a latency greater than 17.5 ns. Then the CL timing is always rounded up to the an even number, however the RCD and RP timings are only rounded to an even number if the timing class ends with an “N”, otherwise those can be odd numbers.

My bad. I think I meant to say CL46. I will update that in my original post.
Edit: I can’t edit my original post anymore

What I was surprised to discover was that the RAM I got was CL40 with JDEC and not XMP