DDR5 6400MHz C38 vs DDR5 6600MHz C32

[HungryHamster]

Do you think there is a major difference between 32GB (2x16GB) DDR5 DRAM 6400MHz C38 vs 32GB (2x16GB) DDR5 DRAM 6600MHz C32?

[BiotechBen]

3 minutes ago, HungryHamster said:

Do you think there is a major difference between 32GB (2x16GB) DDR5 DRAM 6400MHz C38 vs 32GB (2x16GB) DDR5 DRAM 6600MHz C32?

Really depends on if the CPU and motherboard can do those speeds. The 6600 C32 is going to be theoretically faster, but the other thing to look for is first word latency. If the c32 is 28ns while the c38 is 12ns, the c38 may actually come out ahead in day to day tasks.

[RONOTHAN##]

If you're just gonna enable XMP and call it a day, good luck noticing a performance difference, and good luck getting the 6600 MT/s CL32 kit to enable XMP. 

 

If you want to do RAM overclocking, 6400 CL38 and 6600 CL32 are the same memory IC (Hynix M die) and both can do the other's settings. M die is pretty consistent and even OEM sticks can do 6800MT/s CL34 (given an unlocked PMIC), with the only real differences coming down to subtimings, max frequency, and tRCD/tRP, which subtimings aren't part of the XMP profile, max frequency only ranges between 6800 and 7000MT/s so both of those kits should clock the same, and 2 ticks on tRCD isn't gonna be noticeable in anything but SuperPi 32M. 

 

No matter what, you should just get the one that's cheaper, and that will almost certainly be the 6400MT/s kit. Heck, it's probably not worth going for a kit faster than 5600MT/s CL40 since that's also a Hynix bin if you want to overclock (though it's not guaranteed like 6400 CL40 is), and at XMP there isn't gonna be much of a noticeable difference (maybe 5% faster in most realistic tasks, not specific RAM benchmarks).