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Asus ROG STRIX X670E-E problem with POSTing using Expo

Level 8

Hello ROG community, 
I think I found a weird behavoiur of my X670E-E Mainboard.
I just bought a new system with the following components:

  • Ryzen 7950x
  • X670E-E Gaming Wifi
  • LC II 360 cooling
  • Asus TUF RX 7900 XTX OC
  • 6000MHz (2x 16GB Kit) G.Skill Trident Z5 NEO RGB 
  • 2000GB Kingston FURY Renegade
  • Corsair 5000X RGB
  • Corsair RMx SHIFT Series RM1000x 1000W

Newest BIOS 1602 ist flashed.

From the beginning I had the problem that in 1-2 out of 10 reboots or cold starts, my comoputer won't POST. Mostly I received Q code 46, sometimes 0d or 00.
If POST was successfull, system was always stable while running. It also passed various stress tests.

I never had POST problems with the EXPO profile I or II deactivated. Only with the EXPO profile activated.

I contacted the support of my OEM and Asus as well as AMD.
I finally found out, that the key was to change 1 voltage setting.

My RAM runs at VDD and VDDQ voltage of 1.35v.
In the bios I saw that my CPU VDDIO / MC voltage remained at around 1.13v even with EXPO profiles activated. The setting was "Auto".

In the web I read that the VDDIO / MC voltage must be increased by the mainboard while using EXPO profile. This does not happen in my case automatically.

So I manually set the VDDIO / MC voltage for the CPUs memory controller in the BIOS to 1.2v. No other voltages were changed. And since then: No instabilities, no POST problems at all.

This is good news, but there are two reasons why I am posting this:

  • For others who have the same problem to maybe find an easy solution for POST problems with identical hardware
  • To receive opinions from the community regarding:
    Is it a BIOS version bug or a normal behaviour of the board? Might it be a hardware defect that my systems needs more voltage for the memory controller than my mainboard assumes under "Auto" settings?
    Is 1.2v for VDDIO dangerous in any way or ok?

Thanks a lot for your help in advance..


Tuning for CPU signal variance when it pertains to memory overclocking comes down to alignment and using more voltage is not always the answer.

13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090