I'm literally running into the exact same issue right now. Just picked up my new 4090 and came home to install it in my new build which, like you, is a 13900k, Z790 Classified and 64GB of ram.

My first issue is that I can't even access the internet. The LAN and WiFi drivers I had predownloaded from EVGA don't actually have any installers that I can run...so I'm stuck there.

Anyways, I decided I'd install the newest Nvidia driver which I had also predownloaded and while the screens initially flashed as if they worked, they quickly went black and sent my system into a boot loop where every time I log into windows they will pop up correctly and within a second go black and restart again.

I have no idea what to do...

I'm hoping you can get into BIOS for some extra information:
 
Do you have "fast boot" disabled in the BIOS? I have heard many stories over the last couple years of "fast boot" not playing nicely with high-end hardware, and even worse when there's a hardware change.
 
Also, it might be good to go in and double check that the BIOS properly recognizes the 4090 and that the PCIe slot is set up correctly. You can manually set the PCIe gen and it may be worth testing with gen 3 or gen 4 manually set just to see if it performs differently. If it does help and you can get back into Windows, you may be able to re-install the driver, or a vBIOS for the graphics card that may help the motherboard identify and set it up properly.

Neurodrive
I reinstalled Windows and was able to get the internet squared away which downloaded a generic video driver. Seemed to work ok for a minute and then right back to black screens and bootlooping. In the bios I turned off fast boot and set the PCIe slot to Gen 4 manually, but upon reboot I did not get any further before black screening again.

I'm not seeing anywhere in the Bios that would call out the 4090 by name. Is there a particular spot I should be looking?

Try Gen 3 just to see what it does. In the upper right corner of the BIOS, it should show like 7 pairs of boxes and one should show you x16 with 4.0 below it. only 2-3 will be lit up and the others grayed out. Is that what you're seeing? (I'm referencing an earlier motherboard BIOS, but I believe the interface is the same). Also, in the PCIe menu where you would have set the gen 4 manually, it should indicate something like "x16 Gen4" above one of the PE # drop-down menus. I don't know if there's anywhere that it gives the model number in the BIOS, but the fact that it identifies the presence, and correct gen/speed is helpful.
 
Also, are you using a riser cable?

Neurodrive
Yeah I'm seeing what you described. x16/4.0 on the main bios screen and in the PCIe menu I see PE1 as x16/Gen4.

I'm not using a riser cable, this is direct into the motherboard slot.

OK. well, that's some of the low hanging fruit out of the way. You could try to reset your BIOS to defaults and set up your settings again just to see if it helps. It seems like the driver install did something to your windows, but you can't get in to Windows so I was just trying to see if there was anything in the BIOS that was giving helpful information.
 
Can you describe the restarts with any more details on fans, noises, etc.? Are they very calm, or is there a click sound from the computer like the power supply just decided it wasn't interested anymore, forcing the reboot? Some "black screen" reboots come with a ramp-up of GPU fans to 100% while the screen goes black, then the system reboots.
 
I'm asking because some reboots are because Windows is corrupted. Some happen because of a power or other hardware issue.

I think I'd put in a service ticket with EVGA at this point. I know there were a variety of issues with some other 4090's and their motherboards, so they may have some further suggestions for you.

Same here fans are not min/maxing on start up. 
 
New development, I cant get to Bios with 4090 installed but I can with 1070. With 4090 the screen stays black when repeatedly pressing delete key to get to Bios. Post code sits at A6 and I get black screen after spamming delete key. Tried generic keyboard and mouse and have nothing else connected to computer besides ethernet cable and speakers. If I don't hit delete key I can get to Windows login before the black screen reboot. Tried another port on 4090 with same issue. 
 

Neurodrive
The restarts seem to be "calm". I don't hear any clicking or anything ramping up...you just see the screens go black and then the system restarts.

I edited my prior reply when it was probably too late, but I mentioned that my power supply is an EVGA 850 T2 and it's one I pulled from my prior build so I know it works. Everything I've seen suggests that a high quality 850w should be sufficient for a 13900k and 4090.

I may have to put in a ticket but I'd be surprised if they magically come up with some solution, especially since both Nvidia's driver and a generic Windows video driver both lead to black screen/reboots.

I don't think I'd agree with that statement about an 850W with an EVGA z790, 13900k, and 4090 lol. I don't have any specific reason to think that's your issue. I know booting into Windows the 4090 shouldn't be doing anything to draw too much power, but there is a part of boot-up where it cranks the CPU and a 13900k in an EVGA board can draw quite a lot when left on defaults, and even more if you OC it. I've seen 330-400+ in cb-r23, but you really shouldn't see that during a boot-up lol. I would just be quite leery of a 600W GPU, a 300W+ CPU and literally any other parts all on a power supply rated less than that. I would think wkoger71's 1200W would be totally fine though. Again, I don't see how this is the issue in this case, but power supplies tripping OC protection are one source of unexpected reboots so that's how I got to the topic. The only way I could see that happening here is if the driver you installed causes some kind of weird overshoot during boot-up. Even if it did though, I'd be surprised to see the RM1200x also have the same issue.
 
This definitely seems more like a compatibility or driver issue, but testing the GPU in another system is a great idea.
 
One other question, do you have ELEET, HWiNFO64, Afterburner, and/or others booting with Windows? I'm curious if something is trying to hook into the GPU's sensors on boot-up and glitching out since the driver update. I'm not sure how you'd roll back the driver if you can't get into Windows. The classified board does have "mini-DisplayPort 1.4 + HDR via USB4 Type-C ports" that can utilize the iGPU, but that doesn't seem like a common cable that everybody has. You may have to remove the 4090 while you do that to get into Windows and roll back the video driver. You may also want to check on the Nvidia forums and see if others are having this problem. Could be a glitch with this driver, possibly. 

OP are you using 2x32GB sticks or 4x16GB sticks of DDR5 RAM?

Ravenmaster
OP are you using 2x32GB sticks or 4x16GB sticks of DDR5 RAM?

I am using 2 sticks of 32GB DDR5 in slots 2 and 4. 

Update, I can get the computer to start with the RTX 4090 while in safe mode so this has to be a driver issue I would think. Ran DDU to erase all Nvidia drivers. Computer restarts and runs with display adapter listed as Microsoft basic display adapter. In bios I see card showing as X16 4.0 so it sees the RTX4090 I believe. But, as soon as I load any Nvidia drivers back to same issue. I tried drivers 522.25, 526.98, 527.56, 528.49, and now going to try 531.18 after I finish this post. 
 
In Bios I have now switched Primary Display from Auto to PEG. Internal Graphics from Auto to Disabled. USB4 to Disabled. CSM is set to Enabled. Resizable Bar to disabled. 
 
Computer restarted and I'm able to get to desktop now with generic display adapter. Desktop resolution is limited to 1920X1080 and 64Hz refresh rate for my Samsung Odyssey 49" 1000R Curved Dual QHD 240Hz monitor. I need my screen resolution and refresh rates better than this. 

I'm no further ahead either. Pretty frustrated and it's not like I have random other parts to just try things out without spending more money. Not sure why it is that for as much as technology keeps pushing forward, things just can't work out of the box anymore.

B0baganoosh
If you can get into windows with the generic driver, have you tried updating the gpu's VBIOS?

GPU has Bios version 95.02.20.00.01 also ran Nvidias GPU UEFI firmware update tool. 

Not that I think it'll help, but they just released 531.29 drivers today.
 
I completely understand the frustration. I spent weeks trying to debug an issue with my z690 and 12900k (former CPU) that may have been me over-tightening the CPU block (90% sure that was the primary culprit), but it presented in an odd POST code that would just randomly show up and have fits that wouldn't let me boot the computer. Every time I thought I had it figured out it would come back again. You end up trying 100 things before figuring out which stupid thing is causing the issue. In that case it was likely me lol.
 
In your case, I'm wondering if there's a Windows glitch with newer drivers on an older Windows version (even if it isn't really that old). Is your Windows also fully up to date before doing the Nvidia driver? I know you had reinstalled Windows, and I'm curious if it installed the driver before some Windows update (which definitely shouldn't matter, but you know how one update can kill another...or Windows installs a bad driver because it's "helping") and I'm curious what would happen if you let Windows finish all of its updates before letting the Nvidia driver install.
 
It's also interesting that you both have different 4090's, power supplies, memory, but share the same motherboard and SSD and have seemingly the same problem. That definitely does make me think there could be some kind of compatibility issue with the motherboard, hence suggesting a ticket with EVGA...especially after all the people with 4090 issues on the z690 series (and maybe z790 as well? I can't remember).

B0baganoosh
Not that I think it'll help, but they just released 531.29 drivers today.
 
In your case, I'm wondering if there's a Windows glitch with newer drivers on an older Windows version (even if it isn't really that old). Is your Windows also fully up to date before doing the Nvidia driver? I know you had reinstalled Windows, and I'm curious if it installed the driver before some Windows update (which definitely shouldn't matter, but you know how one update can kill another...or Windows installs a bad driver because it's "helping") and I'm curious what would happen if you let Windows finish all of its updates before letting the Nvidia driver install.
 
It's also interesting that you both have different 4090's, power supplies, memory, but share the same motherboard and SSD and have seemingly the same problem. That definitely does make me think there could be some kind of compatibility issue with the motherboard, hence suggesting a ticket with EVGA...especially after all the people with 4090 issues on the z690 series (and maybe z790 as well? I can't remember).

My money is on a compatibility issue between the MB and GPU or a faulty PS. Since this is a new build I have tried both Win11 and Win10 with both experiencing the same issue. Even tried installing GPU drivers before and also after windows updates on both OS with same results. 
 
At this point I am going to try to move the PS and GPU to another computer (Z299 Dark) and see how that goes. 

Got to wonder if the issue of people being able to play on the PC before crash is due to an out of date firmware on Samsung drives killing the drive before it's time.
Easy to check and update it with Samsung magician soft.
It is still possible to purchase drives that have the faulty firmware off the internet.
Basically the drive with that firmware would only write a fraction of what it should to each sector before marking the sector bad and prevent future writes.

Ah, damn. I was hoping we were both installing Windows to the same drive so that it'd feel like using another drive had a decent shot of working. I'll try it anyways, but not expecting anything different.