All Frequencies Matter!
You have likely heard again and again that when choosing of Zen 5 DDR5 you need to go with DDR5-6400 so you have a 1:1 UCLK to MCLK ratio is incredibly important. TechPowerUp decided to show you just what that ratio does to performance in a wide variety of applications, comparing it to the performance you see when paired with DDR5-7200 as well as DDR5-8000. To test this out they used a Ryzen 9 9950X and a G.Skill Trident Z5 Royal Neo DDR5-8000 16GB x 2 kit at a variety of frequencies and latencies.
Their findings reveal the benefits of a 1:1 ratio along with some caveats. Not all DIMMs are created equal and some Zen 5 DDR5-6400 pairings will end up dropping to a 2:1 ratio, which you should be able to confirm in your BIOS or with a tool such as ZenTimings. The sheer bandwidth of DDR5-8000 comes close to matching the performance of a proper 1:1 setup, but carefully read through the various benchmarks to determine if the extra cost will benefit you.