ASUS ROG Maximus Z890 Hero – Stability Issues and Memory Errors with 4×48 GB DDR5-6400

[Goldfinger21]

Subject: ASUS ROG Maximus Z890 Hero – Stability Issues and Memory Errors with 4×48 GB DDR5-6400 – Inadequate BIOS Support for Advertised RAM Capacity

Dear ASUS Team, Dear Community,
I am using the ASUS ROG Maximus Z890 Hero motherboard in combination with an Intel Core Ultra 9 285K CPU (LGA1851) and a full memory configuration of 192 GB DDR5 RAM (4×48 GB, G.Skill F5-6400J3239F48GX2-TR5S, specified for DDR5-6400, XMP 3.0).
The motherboard is officially advertised to support a maximum RAM capacity of 192 GB. While this configuration is listed as supported in the marketing materials and technical specifications, real-world usage tells a different story.

Problem Description:

• With BIOS default ! settings, the system is unstable or fails to boot when enabling XMP profiles 1 or 2.

• MemTest86 already shows errors during the first pass.

• After manual tuning, including frequency reduction and voltage adjustments, the system becomes stable. Specifically:

  • Frequency: 4600 MHz

  • DRAM VDD/VDDQ: 1.30 V

  • VCCSA: 1.27 V

  • Gear Mode: Gear 2

  • Command Rate: 2T (Auto setting leads to instability)

While this configuration is functional, it is significantly below the specifications of the RAM modules and the advertised capabilities of the platform.

ASUS Support Response: The support response consisted merely of a generic statement that two dual kits should not be combined and that the modules are not listed on the QVL. Both claims are technically unconvincing:

• All four RAM modules are absolutely identical (same type, batch, subtimings, etc.) – they were only sold as two 2×48 GB kits.

• The Z890 Hero’s QVL does not list any 48 GB modules – effectively excluding any 192 GB DDR5 configuration, despite this being explicitly advertised as a feature of the board.

Technical and Legal Relevance: If ASUS advertises a motherboard as compatible with 192 GB of DDR5 RAM, then this configuration must be reproducible and stable under real-world conditions – especially with modules from established manufacturers such as G.Skill.
A support response attributing incompatibility solely to the modules not being on the QVL is insufficient. The root cause clearly lies in inadequate BIOS support for full memory population at high frequencies.

Questions to ASUS:

1. Are there official memory presets or "Safe Profiles" in the BIOS optimized specifically for 4×48 GB configurations?

2. Is a BIOS update planned that improves memory compatibility for full memory population?

3. Which configurations (frequency, voltage, timings) have been internally validated by ASUS for 192 GB DDR5?

4. When can an update of the QVL be expected, particularly with regard to common 48 GB modules?

5. If an advertised operating mode (192 GB) is practically unusable – what is ASUS’ position on returns / warranty in light of misleading technical specifications?

---

I kindly request a factual and technical response, ideally from a qualified technician. As a user with professional requirements (AI/ML workloads), I depend on a functioning and validated platform. If this issue is not addressed in a timely manner, I will be forced to return the motherboard.
Kind regards
P. Simon

[KyleMizell]

I am using a ROG Maximus Z890 Extreme with Corsair 9200 mt/s memory (2 sets of 2x24GB). I have similar issues. I can only run my PC on default settings. If I try to use the AI OC functionality, it has severe stability issues. If I use either XMP profiles my PC gets stuck in a boot loop.

I would really like to get the performance benefits of my memory, and I've hoped for a fix with each new BIOS update, but no good yet. I'm currently running revision 1801.

[MasklessFate]

Are you sure IMC can handle the speeds from your ram sticks?

[KyleMizell]

I am referencing ASUS' specifications for my motherboard:
https://rog.asus.com/us/motherboards/rog-maximus/rog-maximus-z890-extreme/helpdesk_qvl_memory/

Although my Corsair memory isn't (yet) listed, the G.Skill memory is nearly identical. I assume supported memory should operate in a stabile manner when using advanced settings. Maybe I'm making incorrect assumptions here.  This is my first custom built PC in quite a while, so I'm also learning a bit as I go.

[MasklessFate]

Ah I see what you mean now, the speed should work, since it is listed there, but have you checked if anyone tried to use 9200mt/s on that board without issues? I personally don't have it and don't know much about stuff either.

[Sargarepa]

It surprises me that you even found a configuration where 192 GB of RAM supposedly works flawlessly. In any case, I would thoroughly test the stability further.The ASUS ROG Maximus Z890 Hero can typically only run stably with up to 64 GB of RAM at higher memory speeds. The reason for this lies in the physical and electrical limitations of the memory controllers and the motherboard's trace layout. Fully populating all four slots with 48 GB DDR5 modules puts a heavy load on the CPU's integrated memory controller (IMC) as well as the signal integrity on the DIMM traces. This often leads to instability, especially at frequencies above DDR5-4800, unless optimized subtimings and voltage profiles are applied.
If you intend to run serious memory-intensive applications on your system, this motherboard is definitely the wrong choice. ASUS primarily targets gamers with this product line—and as long as the board doesn’t overheat (or go up in smoke 😉 or crash mid-game, it’s considered sufficient. For professional workloads, a workstation- or server-class motherboard with validated 4-DIMM support would be more suitable (e.g., Supermicro X13SWA-TF).Of course, you are free to return the motherboard to ASUS and request a refund. It’s unacceptable to suggest technical capabilities to customers that the product cannot reliably deliver.

[Nate152]

Hello Goldfinger21 and KyleMizell

You are both having issues for the same reason, you are combining two memory kits which is not recommended.

1) Shut down your pc and unplug the power supply.

2) Install 1 memory kit in the A2-B2 slots (2nd & 4th slots from the cpu).

3) Depending on your motherboard, clear the cmos by either pressing and holding the clear cmos buttton for 3 seconds or shorting the two pins of the clear cmos header for 5-10 seconds.

4) Boot up your pc.

Ultra high speed memory may need manual voltage tuning for stability.

[KyleMizell]

I appreciate the response, but disappointed that general consensus is that using 4 DIMM modules isn't supported.  That is definitely not anything that is called out in the documentation.

I am using (2) 48GB kits. I don't feel that is pushing the boundaries capacity-wise.

[inge70]

However, it is stated and shown in the QVL how many modules are supported for each RAM.

Example:

It is also correct that 4 modules are supported, BUT not in mixed operation with 2 Kits and XMP.

For the ASUS ROG Maximus Z890 Hero, these are only CMK192GX5M4B5200C38 and CMH192GX5M4B5200C38 from Corsair.

Here, 4 modules are included in ONE kit.

What you're doing is buying 2 identical kits and thinking they're the same.
But that's unfortunately wrong.
It can work, but it doesn't have to work via XMP.

I thought the same thing once and bought 2 Corsair Dominator kits.
One was CMT32GX5M2B5600C36 and a little later, CMT32GX5M2X5600C36.
The only difference in the serial number is the letter after the 2 in the middle.
Clock speeds, etc., are identical, but NOT the revision (see underlined letters).
But it's still two RAM kits.
I was lucky, though; since my RAM can only deliver a maximum of 5600 MT/s, XMP runs with 4 bars and 5600 MT/s, and Memtest86, from the UEFI, runs stable and error-free.
But it could have been wrong.

In the QVL, kits with 4 modules are listed for the respective motherboard, and only for these are the specified clock speeds actually achieved. But only then.
Everything else is a gamble.

[KyleMizell]

Thanks for all of the additional information. I guess I need to figure out what is better. 96GB @ 5600 (it's currently running stable at this speed) or 48 @ 9200 (I assume I could achieve this by removing one of the kits).  Any recommendations?  This is for a gaming PC.