Unstable system when enabling XMP

[Jeepy31]

Got an issue with XMP being enabled.

With XMP enabled, and when my system is cold (after being off during several hours), I get several reboots or freezes when starting my computer. Once my system is hot (after about 6 reboots), it works flawlessly during the whole day.

My hardware :

- Asus Prime Z790-P

- Core i5-14600KF

- DDR5 Corsair Vengeance - 32 Go (2 x 16 Go) 6000 MHz - CAS 36 => SPD : CMK32GX5M2E6000C36

Testing takes a lot of time, because it only happens after stopping my computer for a whole night, but after several days, I can tell that :

- no problem without XMP => perfectly stable at 4800 MHz

- problem with XMP I and XMP II profiles => not stable at 6000 MHz, where I buy an extension set which is supposed to support this frequency

The RAM Sticks are in A2 and B2, just as is recommended.

Windows RAM test is ok (even with XMP enabled, once my system is hot).

Intel specification for my CPU guarantees DDR 5 until 5600 MHz.
According to the seller and to different forums, this should not be a problem . The seller explains this is the nominal frequency for this CPU, not the maximum frequency.

Thanks for your help

[JohnAb]

You'll see on these forums that there is plenty of advice for getting your RAM stable. Start by resetting you BIOS to defaults and then run RAM stability tests. You probably have MemTest 86 in BIOS which will be good enough for now. Once you know everything  is stable at defaults, then at least you have a good starting point and you will have eliminated another cause like the CPU or the way it's mounted.  

[Jeepy31]

Thanks for your answer.

This is why I did and my system is stable at nominal speed. But I bought an extension kit which is supposed to use 6000MHz memory.

[JohnAb]

OK, good that all is stable at defaults. That should rule out another cause. Getting 6000 with 2x 16GB RAM sticks shouldn't be impossible, but you will probably need to increase voltages slightly. 

Your specific RAM kit isn't listed on your motherboard's QVL list, but other very similar Corsair kits are listed with the same latency, so I think you will be able to get it work. 

If you look through these forums, you will find many posts with RAM stability problems with recommendations for adjustments. I've never needed to make any voltage adjustments, so I'll leave the research to you.

However, you probably aren't far away from being stable at 6000, so if any voltage adjustments are needed, I would try increasing them by small amounts from where they are. The main problem often relates to the memory controller in your CPU, some are better than others. 

[Jeepy31]

Thank you,

Do you think it could also be due to a defective motherboard or ram kit ?

By CPU memory controller, do you mean the hardware or the driver part ?

I will search for information to adjust memory settings. I thought I could simply modify the frequency, because modifying voltage is a little more scary for me.

[JohnAb]

The memory controller is part of the CPU. Probably not defective, they just vary in effectiveness. Yes, you could set XMP and then try selecting lower frequencies, that might be a simpler way of trying to get the memory stable. For example, you could try 5800 and see how it goes. 

[Jeepy31]

XMP + 5600 MHz => BSOD in a few seconds. At least, this is a clear result.

No XMP + but setting 5600 MHz => test in progress => Edit : is stable

Is my second test useful, or is it nonsense to modify frequency without XMP ?

Thanks 

[Silent_Scone]

Setting 5600MT manually without applying XMP will not adjust memory VDD and VDDQ voltage settings input by the memory vendor. You will need to inspect the timings set by the board. If stable, the memory timings and subsets are likely more relaxed which will reduce performance. If stable and not wanting to tune further, might be best to stay put.

[Jeepy31]

Thanks for your answer. I'm sorry, I'm not sure tu fully understand it.

Do you mean that setting frequency without adjusting voltage is useless (edit : was 'useful') ? Is it harmful for the RAM kit or the motherboard ?

Thanks 

[Silent_Scone]

No, I didn't say it was useful, only that those values won't be applied. The memory vendor inputs these for a reason. It's the voltage the kit has been validated to run at the designated timings.

You've chosen to test things this way of your own accord, nobody has asked you to - so it needed to be stated. You've not stated whether the system is stable in doing so.