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4 DIMMs in ROG Maximus z790 Hero - no XMP

Level 7
The specs say that 4 DIMMS and up to 128 GB of RAM are a supported configuration on the ROG Maximus z790 Hero. The manual clearly shows that installing 4 DIMMs is allowed. I read it before I bought the motherboard.

I have purchased 4 DIMMS from the Qualified RAM list:
CMT64GX5M2X5600C40 (Ver5.43.13)

The version on my RAM matches the above.

With the RAM in slots 2 & 4, I can use both XMP I and XMP II profiles to achieve DDR-5600.
With RAM in slots 1 & 3 - I can POST ONLY with the 'auto' profile. Selecting the XMP profiles causes the following issues:
1) Ridiculously long POST times (several minutes)
2) Memory errors in Memtest86 - and is not possible to boot the OS

I have swapped all the RAM, so I know they all are working. The above 2 issues happen when using slots 1&3.

I expect a future BIOS update is coming to allow the use of slots 1&3, or do I have to RMA this motherboard because of bad slots?

My Configuration:
Asus ROG Maximus z790 Hero
4x32 GB Corsair 5600 DIMMs - CMT64GX5M2X5600C40 (Ver5.43.13)
Intel i9-13900K

Level 14
The specs also refer you to the memory support list, or QVL: Maximus Z790 Hero Memory QVL

There are currently no 4 DIMM configurations on the QVL for your board, only 2 DIMM configs are listed (that's the "1,2" in the socket support column). In general, 4 DIMM overclocked DDR5 is problematic on all boards. I don't think any of the QVLs currently have 4 DIMM configs listed, for both AMD and Intel DDR5 boards. Additionally, combining multiple memory kits can make it harder to get them working overclocked.

Does your memory work ok as a 4 DIMM config without overclocking (i.e. BIOS on "load optimised defaults", no XMP)? If so, your board and memory are probably both ok. You can probably do a manual overclock on the memory to somewhere between default JEDEC speed and the XMP rating on the DIMMs; people report 4 DIMM configs working with a reduction in the overclocking (below the XMP speed).

This isn't really an ASUS problem, it's a DDR5 problem. I believe it's a problem for all DDR5 motherboards, not just Z790, not just ASUS. Hopefully it will improve as DDR5 matures, and maybe future BIOS updates might help too. Right now, you can have speed or capacity, but not both at the same time, roughly.

Customer Service Agent
Hello, encrypt1d.

May I ask if you can't boot when all 4 DIMMs are installed? Or can't you set XMP?
Please refer to the image below or page 1–5 of the English version user manual.
When*you only install 2 memory sticks, please install them in DIMM_A2 and DIMM_B2 according to the instructions.

Please also check the memory purchasing and installation guide and ensure all memory modules are from a single validated kit.
Do not combine DIMMs from multiple kits—even if they are the same make and model. Mixing and matching DIMMs can result in failure to boot, and compatibility cannot be guaranteed.
In addition, it is also recommended that you refer to Memory Configurations on pages 1–6 of the user manual.

Thank you.

Update: I spent the weekend testing.

I didn't mention before, I am indeed on BIOS ver 703, with the latest Intel ME update.

I define "it works" by being able to pass the memtest86 tests (4/4) in the BIOS.

What works:

  • I can mix and match all I want with 2 sticks in slots A2 and B2. It doesn't matter which ones I put in there, it passes memtest86. I highly doubt this is a mixed kit issue.
  • With 2 sticks, I can even get all the way to DDR 6000 with stock timings and voltages using the XMP profile as a starter, so I've eliminated any issues with RAM quality (It's rated for 5600).
  • In general, I can almost always post with all 4 sticks populated without much trouble - just takes a long time.

What does not work:

  • Any attempt with 4 sticks, with any auto/manual timings, voltages, using slots A1 and B1 results in memtest86 failures.
  • Underclocking all the way to DDR 3600 - still gives memory errors.
  • VDD and VDDQ Voltages all the way to 1.4v - still gives memory errors.
  • Setting the voltages to per PMIC as per - still gives memory errors.

  • Active cooling with a fan blowing on the RAM just in case this was a heat issue - still gives memory errors

Still wondering if I should wait for a BIOS update, and hope for some improvement in support for 4 sticks, or if I should try and return the RAM. It wasn't cheap. Also still haven't eliminated the possibility that my motherboard slots A1 and B1 are defective somehow. Back in the day, you could just try them independently, but DDR5 seems to have made all of this so much worse. How might I validate those slots?

Advice on what to do would be appreciated.

BIOS 0813 which came out yesterday (Jan 18, 2023) has definitely improved things.

I have achieved 2 stable configurations so far, which I absolutely could not do before. In case this helps anyone else:

1) All 4 DIMMS populated. AI Overclock Tuner set to Auto, VDD/VDDQ set to 1.3v, DRAM VPP Voltage set to By Per PMIC.

  • This posts at DDR-4800

2) All 4 DIMMS populated. AI Overclock Tuner set to Manual with:

  • DRAM Frequency: [DDR5-5200MHz]
  • DRAM CAS# Latency: [40]
  • DRAM RAS# to CAS# Delay: [40]
  • DRAM RAS# PRE Time: [40]
  • VDD: 1.35v
  • VDDQ: 1.35v
  • PMIC Voltages: [By Per PMIC]

Both configurations POST and boot much faster than on BIOS 0703 and pass memory tests, run stable in Windows so far.
The XMP profiles still POST, but do not pass memory tests, even with voltage tweaks.

I'll call that a win for now, at least I can keep the RAM.
Damn that's a lot of RAM, and a lot of virtual machines.

Disappointingly, the 4 DIMM config ran stable for 3 weeks, and then I started getting crashes/reboots. A quick memtest96 run from the BIOS confirmed the RAM was no longer stable. I've pulled out the sticks in slots 1&3, leaving in 2&4, and everything is rock solid again.

That really sucks, since now I am past the window for returning the extra sticks. Fingers crossed for a future BIOS update.

I am hoping ASUS follows MSI's direction and fully supports 4 DIMM configs in the future:

Same thing for me, impossible to have 4 DIMMS populated with 32Go Kingston Fury 4800Mhz DDR5 bars in each. It was stable the first 3 wekks then started to crash repeatedly.
Even a ticket to ASUS confirmed that it is not supported yet.

I have not tried yet with new bios 0816 that says "Support high-capacity DDR5 memory kits" for now

Thanks guys, for the discussion.

I'm having the same problem, although I haven't done nearly as much testing as you guys. 

I have the Asus Maximums z790 Hero with four sticks of the following RAM:

VENGEANCE® RGB 32GB (2x16GB) DDR5 DRAM 7000MHz C34 Memory Kit — Black

XMP 1 blue screens as soon as I launch a game. XMP 2 blue screens as soon as Windows boots. When I run Auto mode they run stable at 4800 MHz. Of note, even with these settings, I've had 2 instances where the RGB on my RAM sticks freezes and a reboot goes into safe mode then crashes with a memory error. Another reboot and it's like it never happened. Pretty concerning, and if anyone has any suggestions, I'm all eyes!
I've never messed around with manually tweaking RAM settings, but now may be the time. Or maybe I'll just wait for better BIOS. Just FYI for anyone reading this I'm running the latest (at the time of this writing) BIOS version (0904) and the latest Intel ME Firmware ( Don't be stupid like me and do more research before you drop a ton of cash on RAM sticks!

Level 8

I would like to add I was running the setup posted by encrypt1d (see below) on BOIS 0813 with ME version and it was rock solid UNTILL I updated my BOIS to 0904 and ME version to It turned into a real POS and would BSOD within 20 minutes no matter what settings I tried, even with everything set to auto.

I've rolled back to BIOS 0813 but can't roll back the ME version and it's better than it was on 0904 but now with 4 DIMMS and any settings I've tried I get BSOD and freezes that require a full power down randomly multiple times a day. Since I use my PC for work also I've been forced to pull the DIMMS from slot A1 and B1 for now, so disappointing. 

Ran 128GB / 4 DIMMS perfect with the below setting on BIOS 0813 and ME version

  • DRAM Frequency: [DDR5-5200MHz]
  • DRAM CAS# Latency: [40]
  • DRAM RAS# to CAS# Delay: [40]
  • DRAM RAS# PRE Time: [40]
  • VDD: 1.35v
  • VDDQ: 1.35v
  • PMIC Voltages: [By Per PMIC]

I'm running a Maximums Hero z790, 13900K, ASUS TUF-RTX4090 OC Edition, and 4 DIMMS of Dominator Platinum DDR5 5600MHz C40 (CMT64GX5M2B5600C40) well currently I'm only running 2 DIMMS. 

I returned my brand-new PC today Asus Rog Maximus Z790 Hero ATX DDR5 Motherboard, LGA1700 Intel 13th Gen, Z790 Chipset, Kingston Fury Beast RGB 64GB ( 2 x 32 ) DDR5 Desktop Memory, 5600MT/s Speed, CL40 Cas Latency, 1.25V Voltage, 288 Pin, Dual Channel Kit.

I have tried everything but still get BSOD; the best setting got me down to one error on memtest86, but it is still one too many for stability.  I am not trying to overclock or anything spectacular simply want the product / assembled PC to work without BSOD.  Is that too much to ask? I am no computer engineer, but I can help myself a bit, I simply can’t imagine how frustrated anyone is paying rather a high-end price to get something that does not work OOTB.  ASUS – this is how Intel managed to completely lose share price and equity value.  Your brand will get irreparable damage consumers are not stupid and they will hold you to fix the issues. Please do something !!!