This is a long and winding road so I'll try and not be TOO long winded but I'm newly into PC building and I grabbed myself a smoking deal on an ITX verson of the Z390 Aorus Pro wifi (Rev 1), bundled with an Intel i9 9900k CPU. I brought it home threw in an extra Ram kit and confirmed that it posted, yay! The evil genius plan I had was that I would harvest the 9900k from this bundle and put it into my current daily driver(we'll call it the MSI Z390) which has an i7 8700k in it, then I'd bring the 8700k to the Aorus board and build my son a little Fortnite machine. So at this point all parts have been confirmed working. The weekend comes and I remove the CPUs complete the swap my computer boots with no issue but the Aorus will not post. I go through all kinds of trouble shooting with the 8700k plugged in, 1 stick of ram, no sticks of ram, pulling the CMOS batter (which is hard on that tiny board!), nothing is working. Basically when I jump the board the PSU will rev up quick the CPU fan will start spinning, they will both slow down and wind up again, after 1 or two of these quick cycles the cycle gets longer, to where I often got fooled that maybe we were training ram, we were not. I decided maybe I damaged the MOBO or 8700k in the transfer, they both looked great, but I decided to pull the 9900k from the MSI Z390 and bring it back to the Aorus since it had worked there before. I was seeing the same behavior. So I had mostly given up, I unplugged everything, pulled/cleaned the CPU and questioned all of my life choices.
I maybe foolishly assumed that all versions of Z390 boards were able to handle 8th gen chips, but in my trouble shooint adventures it sounds like the Aorus Z390 is known to have some issues when going from a 9900k to an 8th gen chip. I see there are ways to force the Mobo to go to this backup bios through power cycling the board in certain ways, the timing is hard since the board does it's own power cycles but I was able to get into the backup bios, and then updated the bios on the board to the latest version I could find 10a (I am now learning this is a Beta version, but also not the latest version either). Now when I boot up it is working like a charm with the 9900k, thinking I fixed everything I swapped the CPUs back and... it won't post again.
I've attempted the same trouble shooting steps as before, it seems as though I can't get back into the backup bios, or maybe I corrupted it by trying to get into the backup bios with the 8700k installed.
I'm currious if anyone has gone through this process before and might be able to share any insider info. My two AI side kicks have taken me as far as they can at this point. So I'm hoping for a way to either reliably get to the backup bios (harder on the ITX version of the board since there isn't a physical switch, and with the quick power cycles I don't know when to re-jump the board). I've also seen that there is a "Last possible option, might brick your board" option that includes jumping other parts of the board, since I'm almost given up on this board that's looking more and more appealing but I don't love the idea since I know it's a working board I just need to get it to behave.