Howitz

RMx and RMe cables are interchangeable. The row with 3 pins on the connector is all 12V. The PSU side has all 4 12V pins on the connector for the EPS12V cable. PCIe only needs 3, doesn't really matter which 3 it uses. That's why the missing pin is in different spots.

Should be good 😄

looks like it's caused by me locking ratio at 40, it seems to put ryzen master settings all out of whack, but i'll run it this way until i return that crap to newegg since it's the only way to have it not reboot.

Ryzen Master is a turd, I would uninstall it. It will write to the bios, and read from it as well.

Might be the mobo too, the system reboots itself under normal stock processor operation. If i cap it at 4ghz in bios with a 40 ratio then the reboots stop. So something is not handling things to their full capabilities.
 
I have no way to test both separately so i will end up rma both.

I honestly don't know, however my guess is that there are potential negative effects, as this is why the protection exists in power supplies. The thing I don't know is if you can trip the protection enough times that it stops protecting for some reason. I also think that non graceful reboots can potentially cause windows installation corruption. You could try limiting the power budget in an overlooking app for your video card, which would bring the voltage down, technically. But given transients exceed the budget normally, it might not help.
 
Since I couldn't eliminate the possibility of damage, and the potential damage could be monetarily high, I'd just wait the few days until the new power supply arrives. You could put that spare 560 in temporarily, just to see if the reboots still happen, games won't run as great but the computer will run. I'm pretty sure the GTX 560 draws much less power.
 
I rewatched that content piece, the 3080 is particularly mentioned for high transients, not the 3090.
 

Your powersupply voltage table has your max 12 volt rail output as 750w and i think that is where all of your load is pulling from, as you don't have spinning rust, or an optical drive. If you add the wattage numbers for the other voltages it seems that they all add up to that over 30% discussed in the content piece. I don't think you have the extra head room basically.
 
You could try turning off all unneeded motherboard integrated peripherals (USBs, audio, etc) But I have no idea if that will save you any watts on 12v.
 
Also for testing make sure you turn off any auto over locking features on the CPU, like "multi core enhancement" or whatever they call it. I believe some manufacturers leave that on by default still, so you're already sort of overclocking. I'm not sure if that is still something that exists.
 
That could account for why your power draw is higher than PSU calculators estimate. 

Wouldn't that trip under current protection? Hopefully LTT Lab will let us send in "what if" scenarios to see what all happens.

I was thinking of an outage on the 12V DC that the PSU outputs. If the PSU is starting to fail and/or too much current is pulled that would lower the voltage to dangerous territory and create an outage for the motherboard and everything after it.

I would not consider that to eliminate the PSU. You're on a battery backup. That would eliminate wall power outage, unless you think both the battery and the PSU have issues.I think tripping the current protections inside the PSU might not look the same as AC Power loss.
 
Hopefully I am making sense. We've got a prescription stimulant medication shortage in the USA so I'm operating half asleep.

I'm not 100% sure but I think it rules out a power supply issue in terms of outage... If it were just a few milliseconds of outage it would either shutdown or run on the capacitors, but not a reboot. If it's a spike problem from the RTX 3080 transient power then I have no idea what the behavior would be 🤨
 
Hopefully your tests will be positive and your sister can enjoy the GTX 560 for streaming on MySpace. 😏

That single test won't help. If it still crashes, it could be anything in the system other than the GPU. If it doesn't crash, it is GPU or PSU (or the old GPU is bad which would take us back to it could be anything.). The problem is you're testing with two independant variables, instead of just "bad hardware" you're also testing for a"bad combination due to power draw". 
 
Your GPU takes 3x PCIe 8pins, and your PSU has only 2? Does your board also take a 6 pin?
 
Don't mix up EPS 8 pin and PCIE 8 pin they are not interchangeable.
 
You're so close to the limit I'd actually up your PSU regardless. If you're in the Chicagoland area I can go digging through my shelves to see if I have any larger PSUs for testing, but I'm reasonably sure I do not.
 
Sorry for the delay, I'm typing on my phone.
 
If you've got a rig with a larger supply you could temporarily use it in your sister's box for stability testing. Or if your personal rig is less demanding you could put the 750 PSU in it. 
 
EDIT: In this case your single best test would be different psu of a higher wattage. If you're looking for a new PSU, get one with enough PCIE plugs for motherboard and card. (4?)
 
If you do the two psu test you're going to need to manually short the startup pins on the second supply mother board connector to get it to turn on. Messing that up could hurt I think. Do you have an attachment to do that (typically used to cycle a water pump during fill up of a custom loop.

Ultimately we will all have to do it with RTX 5000 cards, you're just a time traveler!
 
In an AC situation I wouldn't recommend it, but with DC 12V as long as you don't mix up the two PSUs on the same card it's fine.

My reading from the rules seems to indicate that since this isn't self promotion, I can post it.
 
https://youtu.be/zG71dQ9qRbc

Or if you have a cheap GPU lying around it could be worth swapping it to see if it keeps happening. Might be less trouble than another PSU.

Troubleshooting is all about removing as many variables as possible 😅

If it's just a reboot, it could be the reset button or any kind of request made by the bios, a device or something. If it's a full shutdown it's more likely power related, but not 100% sure either...

It's probably obvious but... Have you checked that the power switch and reset button pins are well seated on the motherboard? Could the reset button itself be faulty?
I would try to unplug the reset button pins to make sure it's not related to the case.
 
Also, a long shot, but I've seen this behavior in PCs with bad USB plugs making random short circuits.

Have you tried changing in the Bios the behavior of what should the PC do after a power outage? If you can make it so it doesn't restart but keep it shut down, it could help you rule out a few issues.
 
Also try to leave it on the Bios UI for a while, see if it reboots randomly as well or not 😛

My suggestion is RMA just the mobo 🤔

I got mine as an open box but from a microcenter and I could literally check the whole board out at the store. So I pretty much knew what I was getting. 

You need to disable PBO for it not to boost high past where it shows to be stable. My suggestion would be to look toward the PSU. USUALLY it is a PSU issue if it is crashing hard under load.

It gives performance boosts which honestly most people do utilize.
not very familiar with the MSI BIOS, may be in CPU settings.
 
Additionally, with a 5950x and a 3080 I probably would have gone with an 850W but that's just me being an over-builder. 
 
Additionally, with that weird crashing behaviour, I would look into the RAM as well, furthermore, "high frequency" Vengeance and Ryzen can do some weird stuff.

It likely the mobo, CPUs have a very low incidence rate compared to motherboards. Would also keep doing bios updates soon as they launch since this is a brand new platform 

I'd clean the residue off the back if you haven't. That sounds like it could be an issue. When I got my board from Newegg when I built my system it wasn't sticky.