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Asus Rog Maximus Z790 Hero and 128GB Corsair DDR5 6400MHz, Memtest problems if BIOS is updated.

IICIIEII
Level 8

Hello guys,

I am just building a new system with the following specs:

I9 13900KS

Asus Rog Maximus Z790 Hero (came with BIOS 0813)

128GB Corsair DDR5 6400MHz (2 kits of 64GB, CMK64GX5M2B6400C32)

Asus Gforce 4090 Gaming TUF

Corsair AX1600I

A bunch of NVMES (1 Firecuda 530; 2 Firecuda 520), hard drives (2 SSDs and 2 mechanical HDDs) and an ASUS Blu Ray writer.

Think I that after assembling the system I left everything on Auto and successfully passed 3 passes with Memtest. After that, I updated the BIOS to the latest version and, with everything in Auto, Memtest started spitting quite a few errors in the first pass (more than 10). Therefore, I went back to 0813 and I am running Memtest again. So far, it has completed the first pass without problems. Moreover, with no BIOS I am able to boot the system when XMP is enabled.

I would like to know if you have any guess regarding the stability issue and the XMP problem? I was reading around that this board is not terribly happy with 128GB of RAM, particularly if they come from two separate kits. Could it be that I updated the BIOS and I did not update the ME firmware? (I forgot!). I guess that if it is stable with version 0813 I will leave it like that, I do not intend to overclock the system, or anything.

Cheers and thank you!

Alberto

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1 ACCEPTED SOLUTION

Accepted Solutions

Silent_Scone
Super Moderator

Hello,

Apologies for the late reply (seeing as you've already added multiple updates), but combining and mixing memory kits isn't supported by memory or motherboard vendors. This is because memory vendors bin and validate the memory kit in the density in which it is sold. If you combine memory kits the settings in which the kit is validated for XMP are no longer valid. You would need to return one or both of the memory kits and purchase a single kit validated for the density and frequency you are trying to run.

See Intel's chart for DDR5 memory support on Raptorlake. Please note that frequency beyond what is noted here is considered an overclock depending on the configuration as outlined.

 

Intel_13th_DDR5.jpg

 

 

9800X3D / 6400 CAS32 / ROG X870 Crosshair / TUF RTX 4090

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7 REPLIES 7

IICIIEII
Level 8

Soo... regarding the RAM problem, I saw that with BIOS 0813 everything is stable when I clear the CMOS. The first time the computer boots, it does it with a RAM frequency of 3600Mhz and this is OK. It passes Memtest without problems. Sadly, as soon as I exit the BIOS the automatic profile is applied, and it increases RAM frequency to 4800Mhz, which causes Memtest to fail. Therefore, I manually adjusted the frequency to 3600Mhz and re-run the test, but this does not work, likely because even when the frequency is adjusted by hand something else is still different. Do you know how could I keep the values I get right after clearing the CMOS?

IICIIEII
Level 8

Another update, in case it is useful for somebody. I updated ME firmware and the board to the last Bios (1212). I then set the RAM frequency to 3600Mhz and I ran Memtest. If worked fine and this was good. Sadly, I repeated the test and still gave me an error. Due to this, and the low speed I was getting, I decided to try the two 64GB kits separately.

The first one passed all the tests without problems at 4800Mhz (it was a disaster before) and the second kit is currently running. If it passes all the test, I expect both of them to be fine but right not compatible with my current setup in 128GB configuration, which is a shame.

Silent_Scone
Super Moderator

Hello,

Apologies for the late reply (seeing as you've already added multiple updates), but combining and mixing memory kits isn't supported by memory or motherboard vendors. This is because memory vendors bin and validate the memory kit in the density in which it is sold. If you combine memory kits the settings in which the kit is validated for XMP are no longer valid. You would need to return one or both of the memory kits and purchase a single kit validated for the density and frequency you are trying to run.

See Intel's chart for DDR5 memory support on Raptorlake. Please note that frequency beyond what is noted here is considered an overclock depending on the configuration as outlined.

 

Intel_13th_DDR5.jpg

 

 

9800X3D / 6400 CAS32 / ROG X870 Crosshair / TUF RTX 4090

IICIIEII
Level 8

Well, it seems that at some point in my life I grew old and stayed in the old days, when you could combine RAM from the same (or even different vendors) and it worked OK.  Since I think both kits are fine, I will try to return them in good faith and see if the seller exchanges them for a 128GB kit. Otherwise, I guess I will stick with just 64GB of RAM 😞.

Thanks for you reply, I will keep updating if I discover new things, or at least to tell how it went.

No problem. It's a widespread misconception—the higher the density and the faster the frequency the less chance there is of success. Memory vendors don't account for users putting these kits together, there's no end of the possibilities when trying to account for this. That's why it's simpler to stipulate that they are only validated as a single kit, because that is the reality.

9800X3D / 6400 CAS32 / ROG X870 Crosshair / TUF RTX 4090

IICIIEII
Level 8

It is great to know! I mean, I knew that it was like that but, until now, I had never experienced any problem and I did not worry about it. For example, I have a Threadripper with 192GB of DDR4 and it initially had 64GB only. A year later I got an extra 128GB and everything was fine. DDR5 seems way more sensitive in that regard :). I can definitely confirm that, separately, both 64GB kits are all right and actually they pass Memtest at 6400Mhz, as specified by Corsair.

Yep. High density kits at higher frequency can often be quite hard on the CPU memory controller anyway. Adding another kit reduces our chances even further, and some users simply don’t understand why.

The memory vendors don’t account for users doing this, and quite often with DDR5 you won’t find [single] kits validated or sold for the frequency and density you are trying to run because the platform isn’t capable of running them at that speed unconditionally or even at all.

9800X3D / 6400 CAS32 / ROG X870 Crosshair / TUF RTX 4090