Whoa, what's this. A 13900KF on a lowly B-series board, with a 3+ year-old BIOS version. This is all kinds of trouble.
It is vitally important to use the latest BIOS version with this CPU. Old BIOS versions contained
buggy microcode, triggering intermittent spikes of excessive voltage, which eventually cause CPU degradation to the point of instability. And updating to the latest BIOS version only stops the voltage spikes and any future degradation, but it cannot undo damage that has been done. So let's hope the CPU is still fully stable, but you need to update to the latest BIOS version ASAP, it's been 1 1/2 years overdue. There have been many a 13th/14th gen CPU that have been irreversibly deteriorated by the voltage spikes and ultimately had to be replaced by Intel.
Update how-to:
1) Get the latest BIOS. It's the topmost one on the MSI support page for your board.
2) Extract the file and you will get a text file and the BIOS file. Put the BIOS file into the root folder of a USB stick/drive.
3) Enter the BIOS by pressing DEL during boot, go to "M-FLASH" in the BIOS.
4) Once M-Flash (the updater) is loaded, it will show a list of your drives. Select the USB stick and select the previously extracted BIOS file on there.
5) It will ask for confirmation and then update the BIOS. It's fully automatic from there, takes about two minutes.
After the update, you will probably notice higher temperatures and perhaps even a bit lower performance. You can then go by my
Guide: How to set good power limits in the BIOS and reduce the CPU power draw, it describes two steps to optimize how a CPU is running: Step 1), setting proper power limits for your system, and step 2), lowering a setting called "CPU Lite Load", for huge benefits in lower voltage, lower power draw, less heat, and even higher performance within the power limits.
The problem with step 2) on a B-series board is, it cannot work to the full extent, often you can only lower the setting to Mode 10 or so, not much lower. Only on a Z-series board it would work fully. So for now, you should update the BIOS, and then at least set proper power limits for this monster CPU. This shouldn't be on a B-series board to begin with, it's ill-equipped to deal with an i9. But I get it, slim pickings for good micro-ATX boards sometimes. Although back when you bought it, there were better Z-series µATX-sized boards readily available.
