B0baganoosh
 
That is definitely interesting and sounds like a BIOS bug to me. I wonder if on Auto, it they were enabled, which was causing an issue with legacy boot (I think those require EUFI to work)...then when you disabled and went back to "auto" they were still disabled. So "auto" just left them in some previous state instead of switched them based on the other settings and hardware. Just a theory. If you leave them manually set to disabled, does it continue to boot correctly or was it just an intermittent chance?
 
Similar to your plan, I bought a G6900 trying to test out the 7F code issue I was having and it worked perfectly fine (compared to the 12900k I couldn't get to boot right 100% of the time).
 
As for comparisons with the Dark boards, I think the Classified boards are just a little thinner with a couple less copper layers so they might flex just a little more, which makes them more susceptible to uneven tightening. You're probably right that it isn't the issue, but it is something physically different between those boards and another reason I bought an aftermarket back-plate for behind the motherboard to stiffen things up on my z690 Classified. I'm going off memory from z690 announcements (can't remember z790 honestly) so I could be mistaken there.

Yeah i think I'm going to reflash the bios next and see if that helps. Also try other bios switches. 
 
The other weird thing is originally when i first went from uefi to legacy, i couldn't boot without also setting above 4g and rebar to disabled. After i DID get it to boot with those 2 disabled and legacy boot, i randomly had D4 boot failures even after multiple successful posts. This time though, i was able to hit reset and it posted the 2nd time. This is in contrast to earlier when i first set it to legacy it would get stuck on D4 until bios wipe and reboot/power off didn't fix it. 
 
Only other thing i could think of is the Z790 classified doesn't like my evga 980 ti classified. I've had other weird issues with it on my X299 Dark where there's no display out until Windows successfully posts. (No bios screen, etc) But will display perfectly after Windows boots and Nvidia drivers come up. There i had to use an old 8400 gs and it would display just fine. I'm starting to think it also could be an issue with loading the 980 ti upon post. 

FAQ: https://www.evga.com/support/faq/FAQdetails.aspx?faqid=59772
 (excerpt)

How to Enable Resizable BAR Support in EVGA Motherboards:

For compatible EVGA motherboards, you must enable the "Above 4G Decoding" and "Re-Size BAR Support" settings, and disable "CSM Support".  A full walkthrough of how to change these settings can be found below.

• Note 1: The CSM Support option is available only if your Windows installation is configured for UEFI.  If the motherboard Boot mode select must be set to Legacy, then you will be unable to enable Resizable Bar support.  Although a full walkthrough of installing Windows in UEFI mode is outside the scope of this FAQ, here are a couple Microsoft documents that discuss the issue in more detail, along with a way to convert your hard drive from a legacy install to a UEFI install:
  • https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/windows-setup-installing-using-the-mbr-or-gpt-partition-style
  • https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/boot-to-uefi-mode-or-legacy-bios-mode
• Note 2: Changing your CSM Support setting can affect your ability to boot into Windows.  The Compatibility Support Module is designed to allow you to use the benefits of UEFI with hardware that may not be UEFI compatible.  Disabling the CSM is necessary for Resizable Bar support, but you may find that older hardware may not be compatible with CSM disabled.  Although a full discussion on this topic is outside the scope of this FAQ, you may be able to resolve the issue through simple troubleshooting, such as a firmware update to the legacy device, or you may determine that your legacy device is simply outdated; it may be time to find a newer product with UEFI support.

 

Disable "CSM Support"

Go into the Boot menu.  Make sure your "Boot mode select" is "UEFI".  If you normally boot into Windows using "Legacy" mode, please see Note 1 above, as you will be unable to properly enable Resizable Bar support.  If the Boot mode is instead set to UEFI, you should see a menu further down called "CSM Configuration". 



 CSM & Fast Boot ---> Must be off --- to turn CSM Off you want to use UEFI

 
Ask EVGA if the 980Ti Classy has a UEFI updated BIOS  --->  Please contact EVGA Support at Support@EVGA.com
 
Make sure you load "default bios settings" before you flash your BIOS - many people seem to skip that step
 
https://forums.evga.com/FindPost/3407542   (excerpt below)
 
Since things are a little complicated with a lot of threads spread all over the place, I'm going to post all the relevant BIOS information we've given to people.  If you don't see a BIOS you need, you can request it below.  However, I'm making this thread mostly to inform people about some of the issues people run into when flashing their BIOS or having to update the MCU via Precision X1, so new BIOS additions will be a lower priority.
 
PSA#1: TURN OFF "FAST BOOT" IN YOUR MOTHERBOARD BIOS.
PSA#1: TURN OFF "FAST BOOT" IN YOUR MOTHERBOARD BIOS.
PSA#1: TURN OFF "FAST BOOT" IN YOUR MOTHERBOARD BIOS.
 
Longer PSA in spoilers.  I strongly suggest that you read this at least once.  It could prevent an RMA.  Seriously.
 

Once again, turn off Fast Boot in your motherboard BIOS while you're playing around with flashing your BIOS.  If fast boot is enabled, Windows will treat your card as the same GPU unless there's an obvious change, such as you change from a GeForce RTX 3080 to a GeForce RTX 3090, for example.  Otherwise, Windows will just assume that nothing in your system has changed, including the DeviceID, which will change when you flash to a different BIOS version.  Because Windows doesn't update the information automatically, it will give Precision X1 the wrong information, which is how many of you have run into an MCU flashing issue.  If fast boot is disabled, Windows should check the DeviceID of each hardware component during each boot.  It's still worth it to restart a couple times after flashing or flipping the switch over to a different BIOS to make sure everything is working normally. 
So, please make sure to turn off Fast Boot until you are done flashing, and you've decided on which BIOS switch you want to use.  At that point, you can restart and re-enable Fast Boot again, if you wish.
close
 
PSA#2: DISABLE CSM IN YOUR MOTHERBOARD BIOS BEFORE FLASHING A REBAR BIOS.
 
Longer PSA in spoilers.  If you forget to disable CSM in your motherboard BIOS before flashing a ReBAR BIOS, then you may end up with a black screen upon your next boot.  If you need to learn how to enable NVIDIA Resizable BAR, visit our FAQ: https://www.evga.com/support/faq/FAQdetails.aspx?faqid=59772
 
Spoiler