Hope OP can boot from 9900k. XPS8930 was first released in October 2017, original stock 8th gen. 9th gen i9-9900k or i7-9700k was released 1 year later in October 2018. Re: all BIOS revisions since around November 2018 included the 9th gen microcode.  correct. Early 8930 bios 1.01-1.013 (up to Aug 2018) did not support 9th gen. In Nov 2018 bios update 1.1.3, Enhancements: - Enhanced to support Intel i9-9900K, i7-9700K and i5-9600K processors. Q: Z370 chipset cpu OC features locked/ grayed out in XPS 8930 bios? A: community user reported it is not grayed out, but apparently quite limited. It is a known fact mainstream oriented Dell XPS is not ASUS or extremely friendly to overclocker.  average XPS user may get an iota of OC without freedom to wreck the system. service manual for system setup: 
I upgraded my CPU i5-8400 to i9-9900k. Bios was latest 1.16...  Plugged in PSU and get 2 blinks followed by 3 blinks.  I checked all connections and I was very careful with the CPU. Any ideas?
XPS 8930, i9-9900k CPU upgrade, failed