Reported even on AM5, you can only get 6000 Mt/s with 2 sticks, attempting to run all 4 slots on most boards won't work unless you slow them down to base JEDEC speeds.

Can confirm, had this issue on an ASRock DeskMeet X600.

Really? I'm running 4x 24GB sticks at 6000 with no issues. These were on the certified list for the motherboard.

https://valid.cpuid.com/sdyce7k2

4 x 32GB G.Skill Flare 6000CL30 are running on Asus TUF B650E with 6000CL34

AM5 is 3600MT/s for 4 sticks; check the specification of a CPU of interest to you, expand the Connectivity section. For 2 sticks it's 5600MT/s. The Ryzen 9 9950x3d officially only supports 5600 or 3600.

https://www.amd.com/en/products/processors/desktops/ryzen/90...

Obviously, you can run memory faster than the officially supported speed, including 4 DIMMS, but the Zen 5 architecture has a reputation for being finicky trying to run 4 DIMMs at higher speeds and you need a bit of care in what you pick and how you tune it.

I'm running 8000 in 2:1 on my 9800x3D. Slightly better than 6200 1:1 on here, and basically the same as 6400 1:1, but easier to dial in at 8000.

Side note: At 2ghz IF, a single Zen4/5 CCD can saturate 7200 MT DDR5, but the io die is not restricted to that, so x16 and IGPU DMA can still saturate it at 8000.