I went from a 7700K on my last game PC to a 9900K on my new game PC and the difference is very apparent in the game even though I had my 7700K overclocked to 4.5 GHz.
The difference is all the z390 board manufactures auto overclock straight from the factory with MCE (Multi-Core Enhancement) so the lowest the 9900K goes is 4.7 GHz (24/7) when under load and boost up to 5.0 GHz when needed with 2 cores.
The only way you can get all the z390 motherboards to drop to Intel's normal Turbo boost of 100 seconds max per core (with 3.6 GHZ base versus 4.7 GHz base) is by turning OFF the MCE, with makes little sense since it's really nice to have all the extra power without using any more Vcore than the 7700K uses normally too (1.200 V).
This is why the 9900K is so much nicer than my old OC'ed 7700K CPU.
But MCE has been around since 2012 in various names by different companies...and has been available on motherboards/chipsets for CPUs going at least as far back as Ivy Bridge, to include the 7700k. Pretty sure it is optional now as it was then.
Basically overclocking for people who don't understand overclocking. Maybe easier, but like all "automatic" BIOS overclocking, not necessarily better than a properly applied "manual" overclock. (I'm sure there's a reason it can be turned off, and that reason appears to be higher voltage than needed and the resulting thermal issues...there's a lot of discussion about this online. It seems that many experienced overclockers turn MCE off to get better thermals at the same or better speeds.)
Incidentally, the board listed in Hellshade's profile (MSI Z170
GAMING M7) supports MCE on CPUs back to Skylake, including the 7700k he's using. I suspect all performance boards that support those CPUs feature some form of MCE, albeit by different names perhaps, meaning your prior 7700k setup probably had it too. Some have it turned on by default, some have it off. And although I'm not familiar with the details right off, I would imagine the 7700K's higher base speed would mean that it's MCE will follow (i.e., might be higher than the 9900k, as Hellshade asked about). Again, that's not based on first hand experience but it would make sense.
