[SOLVED] Downgrade BIOS for Zen 2 after Upgrading for Zen 3

[Bongert]

I recently got a Zen 3 CPU, the 5800X3D, and put it in my old motherboard, the MSI B450 Gaming Plus (non Max). I upgraded from a Zen 2 2600 non-X CPU so in order to install the new Zen 3 CPU I had to update the BIOS, which I did and everything worked flawlessly.
Now I've gone and bought a new motherboard which will form a completely separate system with the 5800X3D.
Now i want to put my old Zen 2 2600 CPU into my old MSI B450 Gaming Plus motherboard to basically redo the system to the state it was before the upgrade. You would think that the updated BIOS would simply work with both the old and the new generation of CPUs but apparently it doesnt as my system boots but doesnt display anything.
I tried removing the CMOS battery to clear the BIOS but that didnt help either.
What am I doing wrong? Is it not the BIOS after all? I tried all kinds of stuff already that is being suggested when googling for "pc turns on but no display".

 

[Colif]

new BIOS should work with old CPU as there are no restrictions on mb site - https://www.msi.com/Motherboard/B450-GAMING-PLUS/support
they just added support, didn't remove it.

So possible problem isn't bios.

try remaking it, perhaps you need to check cables inside are secure.

 

[Bongert]

new BIOS should work with old CPU as there are no restrictions on mb site - https://www.msi.com/Motherboard/B450-GAMING-PLUS/support
they just added support, didn't remove it.

So possible problem isn't bios.

try remaking it, perhaps you need to check cables inside are secure.

before i go and rip everything out and back in again: a faulty CPU would not let the system boot at all would it? when i power cycle the system the fans momentarily ramp up to 100% and then calm down again, so that would mean it loads the automatic fan profile instead of being static. that would mean the system actually does fully boot and its really just a display issue, right? i can also hear the hard drive making noises, though thats not where i boot from.

 

[Bongert]

new BIOS should work with old CPU as there are no restrictions on mb site - https://www.msi.com/Motherboard/B450-GAMING-PLUS/support
they just added support, didn't remove it.

So possible problem isn't bios.

try remaking it, perhaps you need to check cables inside are secure.

i tried reseating every connection now, which didnt help. I tried updating the BIOS again which did the trick. but its weird since it didnt work the first time with the updated bios and it didnt work with the flashback BIOS.
thanks anyways!