Memory help


Posts: 7   +1

I need some advice with regards to RAM for a new build.
The core build in question will be the following :

CPU - Ryzen 7 5800x
Mobo - MSI MAG X570 Tomahawk Wifi
GPU - Radeon 6700/6800
M.2 - Samsung 980 Pro 1TB
PSU - EVGA supernova 650 G3 (already have)
Cooler - Noctua NH-D14 (already have) may get a new black one, smaller one, and give this away
Case - Fractal Design R6 (already have)

I want to put fast RAM in it but my knowledge doesn't stretch far enough to do this correctly. I understand that I need a low CAS latency (lower the better apparently) and I've been looking at the QVL list for the mobo. This is where my doubts creep in. G.Skill RAM (which is what I really want to use) seems to go as low as CL15-16-16-36 on a 4000Mhz kit. However, on the QVL list the lowest supported 4000Mhz kit is CL18.
My question is obviously going to be can I run the CL15 kit without any issues?
If so, would I need to adjust anything in the Bios to get it working correctly (full capable speed)?
Also if my understanding is correct so far?
Is there an even faster kit that I just haven't found yet?
How high can I realistically go with regards to Mhz where cost to performance trade off just isn't worth it anymore on this platform?

Apologies for the noob questions but I could do with your advice on this matter.
Many thanks.


Posts: 1,075   +664
Don't bother to look at QVL lists. No use for them. Just make sure memory is basically compatible (no DDR3 sticks to DDR4 slots etc). That's about only use QVL lists have.

For memory speeds, depending on price, somewhere between 3200-4000 MHz sticks should offer best price/performance ratio. Unless planning to heavily overclock, there is no real reason to go above those. 3200 MHz is fastest "officially" supported btw but most motherboards support well above that.

You must adjust memory speed on BIOS, perhaps memory modules have XMP or other profile ready you must choose.


Posts: 7   +1
Ah great.
In that case I shall go for the G.Skill 4000Mhz CL15 kit I found.
Although it looks very much like I'll be waiting for these ridiculous GPU prices to calm down first.
Much appreciated advice.


Posts: 481   +110
TechSpot Elite
This looks like a gaming rig so you won't see much benefit of faster memory. When you game you are GPU bound, which means that the CPU is hardly working when you game and it is the video card that limits your framerate. Check this video out that also touch on 2 and 4 sticks:



Posts: 7   +1
Since starting to research and improve my knowledge of RAM I have discovered these knowledgeable Australians . Also Gamers Nexus and was recommended Buildzoid.
Between these three my understanding of RAM is vastly improving.
RAM was always my grey area.
Many thanks for the advice, really helped me.
Chris .