Ryzen spec vs motherboard QVL

therealdippy · 10 Apr 2021 at 14:32

From what I have read, AMD specify Ryzen (I'm considering 5900X) at 3200MHz, but people are generally getting it working at 3600MHz, and some people higher. I'm keen to use memory which is listed on the motherboard QVL, which leaves me at a dilemma. For the configuration and manufacturer I'd like to choose, I can find 3200MHz C16 sticks listed on the QVL but not 3600MHz. The next I see is 4000MHz C19 and the price difference is not that much for me. So I am inclined to buy the 4000MHz C19 sticks which are on the QVL, and if I understand latency properly (?) as long as I can clock at more than about 3400MHz they should still have a speed edge over 3200MHz C16. Obviously if I get a CPU that can be stable at 4000MHz great, but are there any consequences of running that memory below 4000MHz?

Cooler running · 10 Apr 2021 at 19:28

Your QVL parts are likely older as they do the testing before the product is released and are extremely conservative. QVL's are usually only for server customers or large organizations, as it's a convenience for IT guys to just tell their supplier to send over replacement RAM without having to do any research into which sticks will work.
I haven't heard any stories of 3600 having issues, and doubt it would have unless you have a A520 board or bargain-bin B550.

4000 CL19 will likely be a little faster than 3200 CL 16, but not by a huge amount.

are there any consequences of running that memory below 4000MHz?

I'm currently doing it with my 3600 CL 17 sticks, running them at 3200 as they are on a b350 board. It almost certainly will be fine, but it somewhat defeats the object of using QVL products.

therealdippy · 10 Apr 2021 at 19:36

Thanks. Maybe I'm worrying about QVL too much then. Is 3600MHz CL16 the better choice?

Cooler running · 10 Apr 2021 at 19:41

therealdippy said:
Thanks. Maybe I'm worrying about QVL too much then. Is 3600MHz CL16 the better choice?

I've usually found that lowering 1 cas latency roughly equals 1 step up in clock speed; so it's about the same or maybe a little faster than 4000 CL 19 but not by much. From what I understand the infinity fabric ratio makes 3600 the "sweet spot" but that still only makes an almost immeasurably small difference in overall performance. 4000 CL 19 should still be faster than 3600 CL 19.