RAM choice - higher freq or lower latency?

[jak3676]

I'm interested in the community's thoughts on RAM.

I've got my choice pretty much narrowed down to 2 nearly identical sets of G.SKILL Ripjaws V Series 32GB (2 x 16GB) 288-Pin DDR4 SDRAM. The only difference is 3600MHz and CAS 16 vs 3000MHz and CAS 14. They're basically the same price. I'll pick up 2 kits (4x16GB for 64GB total).


https://www.newegg.com/g-skill-32gb-288-pin-ddr4-sdram/p/N82E16820232907?item=N82E16820232907
DDR4 3600 (PC4 28800)
Timing 16-19-19-39
CAS Latency 16


https://www.newegg.com/g-skill-32gb-288-pin-ddr4-sdram/p/N82E16820232226?item=N82E16820232226
DDR4 3000 (PC4 24000)
Timing 14-14-14-34
CAS Latency 14


I'm running a mildly overclocked i9-9900k, on an ASRock Z390 Phantom Gaming 4 motherboard. The MB says it will support up to 4300MHz, but anything over 2666MHz is considered an overclock.


Neither SKU actually appears on my MB's supported page (https://www.asrock.com/mb/Intel/Z390%20Phantom%20Gaming%204/index.asp#Specification), but they do support similar capacities/timings/frequencies. I acknowledge that I'm taking a bit of a roll of the dice either way. But the MB is ~2 years old, and these are newer RAM SKUs. So I think I'll be OK, but if anyone sees something I'm missing, let me know.

[Wizeowel]

Is not an either/or.

CAS latency is measured in the number of clock cycles, so the latency is dependent on the frequency.

You can convert to nanoseconds to get absolute latency.
The F4-3600C16D-32GVKC kit has CAS latency 16 and frequency 1/3600, multiply to get 4.444 ns absolute latency.
The F4-3000C14D-32GVR kit has CAS latency 14 and frequency 1/3000, multiply to get 4.667 ns absolute latency.

So the F4-3600C16D-32GVKC is faster and more responsive.


Edit:
However, regarding the QVL, your AsR Z390 Phantom Gaming4 is listed on the G.Skill product page for the F4-3000C14D-32GVR (see https://www.gskill.com/qvl/165/184/1536044208/F4-3000C14D-32GVR-Qvl) but not for the F4-3600C16D-32GVKC.

[jak3676]

Thanks for that. Soon as you said it I realized I had totally forgotten about multiplying out the latency. Been too long since I actually had to build my own rig. I went with the 3600MHz, should arrive this week.

[WOWBOX40]

I havent bothered to learn how the RAM latency etc work in fine detail, but what i noticed is that going from 3000 to 3600 = my main game "sustained fps" increased by around 7-10. Using the xmp bios profile. *your milage may vary.

[jak3676]

Just to close out this thread I went with the F4-3600C16D-32GVKC kit, everything is working fine - XMP is enabled although I have everything at stock speeds and voltages. Although I ordered 2x 32GB kits (4x 16GB sticks total) and ended up putting 1 kit in my wife's PC - so now I'm ordering 2 more kits.