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RAM Refuses to OC, DDR4-3600 CL18 - CMW16GX4M2D3600C18

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kickasskingy

New Member
Joined
Feb 19, 2021
Hi All,

I have recently upgraded and trying to OC my RAM. My system:
- Corsair Vengence DDR4-3600 CL18 - CMW16GX4M2D3600C18
- MSI Tomahawk X570
- Ryzen 7 5800X (stock)
- RTX 3060 Ti

I have seen many articles on overclocking this RAM and even MSI list it on their QVL with memory presets on the mobo - eg https://www.overclockers.com/forums...o-RGB-2x8GB-DDR4-3600-CL18-CMW16GX4M2D3600C18

Anyhow, I can apply the one XMP profile to the RAM and it is very stable no issue - don't get me wrong I am happy with this, but as an engineer, I can't help but want to tinker and optimise :p

The issue I have is that any timing change I apply refuses to POST? Even worse ones!
I have tried using tools like Ryzen Mem Calc to no POST.
I have tried many Mem Try It! presets on my motherboard... none are stable and only one actually POSTs (but is unstable).
I have tried following many DDR4 OC guides online, including those in this forum.

By fixing the timings to stock and simply increasing the mem frequency to 3800mhz (keeping infinity fabric to 1:1), I was able to get this one OC to POST. All memory benches I throw at it passed and did well!
However, the PC would instantly crash on any CPU bench! This was when I noticed that actually when any Mem OC I try fails to POST it is actually the CPU fail light on not memory!

Why would any memory OC (except the XMP) cause the CPU to fail?

I have tried tweaking the SoC and VDDG voltages but to no effect.

What am I missing here that would mean the CPU hates any memory tweak? I assume I'm being a tard and missing something obvious in BIOS, or the motherboard is doing something silly to a parameter set to "auto"!

Any ideas welcome, thanks in advance :)
 

RJARRRPCGP

Member
Joined
May 30, 2004
By fixing the timings to stock and simply increasing the mem frequency to 3800mhz (keeping infinity fabric to 1:1), I was able to get this one OC to POST. All memory benches I throw at it passed and did well!
However, the PC would instantly crash on any CPU bench! This was when I noticed that actually when any Mem OC I try fails to POST it is actually the CPU fail light on not memory!

Why would any memory OC (except the XMP) cause the CPU to fail?

Yikes, it's acting like the RAM is causing more Vdrop, to the point where there's too low of Vcore, unless it is trouble with the IF. I dunno what it could be.
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
There are more things linked to each other and too high memory clock/IF can cause the CPU to fail tests because the IF clock is too high for something (usually voltages or the CPU simply can't handle it).
I would check 3733 as it's barely slower and usually much easier to stabilize.
 
OP
K

kickasskingy

New Member
Joined
Feb 19, 2021
Thanks all for the input, I did try to fix the IF and voltages but no luck. I got it stable at 3733 as suggested, but the performance difference was within the error of XMP. Realistically, I think if I want to see better perf I need to just invest in a better RAM kit, Corsair aren't as good as they used to be IMO, I also found out I had issues with differing RAM versions on the same product codes - didn't even realise this was a thing, seems rediculous!
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
In real, memory doesn't affect performance as much so it would be worth spending a lot of money on a new memory kit. If you already have DDR4-3600+ at 1:1 IF then it doesn't matter much if it's CL14, 16, or 18. In some cases, dual-rank memory helps a bit but it doesn't mean it significantly improves the gaming experience. It's like a 5% improvement so you won't see the difference anyway. The difference usually comes from the whole setup, if you add all these 3-10% improvements here and there. However, when you already have a modern PC and nothing is causing issues, then only a memory kit makes barely any difference (assuming it's DDR4-3200+ at reasonable timings).
The RAM choice is something that you do before you buy the PC or make a significant upgrade. After that, there is no point to waste money and time, unless it won't let you sleep.