G-SKILL XMP 8800 Mhz Problem

[Ily3ss59]

Hello, I bought the RAMG.Skill F5-8800C4255H24GX2-TZ5CRK and it appears on the QVL list, but the problem is that when I activate XMP I have crashes in the game and I don't know how to adjust it so that it works.

Here is my equipment :

CPU: Intel Core ULTRA 9 285 K

Motherboard : ROG MAXIMUS Z890 EXTREME (BIOS 1703)

RAM : G-Skill 48 GO 8800 MHz 

Thank you for your help 😊

[Chainbold]

I have the same memory, and I had initially also problems to run it at XMP I or II. I step by step lowered the frequency manually (while keeping the XMP timings) until I found a stable spot, which in my case was 8400. Your milage varies, some here are not getting more than  8000MHz, or even less.

I suspected the RAM to be the culprit. But after discussing the issue with GSkill Support, I suspected the IMC on my CPU not strong enough to run the memory at 8800MHz. I changed the CPU, and the memory is now running at close to 9000MHz. 

The memory vendors are hyping their expensive CUDIMM memory without explaining that the advertised speed is only possible when you are lucky enough to have a ULTRA 200 CPU with an above average IMC. By all the "frustration reports" I have seen, I would say that for this reason maybe half of all users will never see the advertised max speed for their shiny CUDIMMs.  

[Ily3ss59]

Thanks for the feedback and the problems you encountered... Ok I'll try at 8733 and if that doesn't work go down slowly

[Chainbold · Accepted solution]

In BIOS 

Advance Mode > Extrem Tweaker > DRAM frequency

If you had set your CUDIMM 8800 for XMP I, the DRAM frequency will show 8800 MHz. There you can change the DRAM frequency, while keeping all other XMP settings. Important is to keep the DRAM voltages at 1.45 as set by the XMP profile. As I said, I would step by step lower the DRAM frequency 8600>8400>8200 etc until you find a stable level, while keeping XMP I timings and voltages. Obviously you can also start from 8000 MHz and go upward and see how it goes. 

Stability testing should be with the free version of OCCT, or  RAMTest from Karhu.  Don't waste your time with the popular MemTest86: It's not reliable. 

[Ily3ss59]

So after several OCCT tests at 8800, 8733, 8600 Mhz where I had errors I found stability for 1 hour under OCCT at 8333 Mhz.

[Chainbold]

8333 is not a bad result for GSKILL 8800, in my experience. I got mine at the same level stable (before I changed the CPU to one with a better IMC). Some user can not get their 8800 above 8000. 

You could maybe squeeze out another 100 Mhz on top, by increasing both DRAM voltages from 1.45 to 1.50. Or you go into "DRAM TIMING CONTROL" and increase latency by changing "CAS" from "42 to "44". 

There are dozens of DRAM subsettings that can be further manipulated. A full guide to do so for the ASUS BIOS is here: https://skatterbencher.com/2024/10/24/arrow-lake-memss-overclocking/

But in my experience, all this finetuning will result in nothing much. With more agressive settings you might boot into Windows, but the system becomes unstable, or you even corrupt system files. 

[ttesty_1]

On a Taichi, you wouldn't have to step down the RAM frequency like this.. I think it's a motherboard limitation here.

[Chainbold]

no, as gazillions of times explained by gazillions of users, it is a matter of your CPU's IMC. Intel has specified to run the IMC of their Ultra 200 series CPU, for a maximum speed of 6400 MHz. Anything above this is lottery, depending on the  quality of your IMC.

[Ily3ss59]

Yes, I find it a shame if it really depends on the CPU's IMC of the processor, I would still test it with future BIOS updates, but hey, changing the processor for that... no thanks.

[Chainbold]

I understand that changing the CPU for this purpose is not exactly convenient, in particular as we never know the outcome of the silicon lottery. But at least I would recommend to evaluate your IMC. That could give you an understanding whether the IMC is indeed the bottleneck. If it is not,  BIOS settings, that you can change, might be the reason that you do not get the memory running at 8800MHz.

To evaluate your IMC you need to go to "AI" and run get "MC SP".  The score you get is indication how good your IMC is. An average score is around "75". Anything below this, could indicate that your IMC is the bottleneck,