Overclocking on the Z390 platform is pretty much the same as on the Z370 platform. So if you are familiar with that, overclocking your 9th gen Intel processor will be pretty easy. We are going to do all of our overclocking in the BIOS.
Getting into the BIOS you are going to want to set the “OC Explore Mode” to Expert. Then set the “CPU Ratio Apply Mode” to all core. For the CPU Ratio set this to what you are shooting for. We are shooting for 5.1 GHz so our ratio will be 51. Also if you BCLK is not set to 100.00 set it to that.
Moving down the page you are going to want to set your “CPU Core / GT Voltage Mode” to Override Mode and set your CPU core voltage. For 5.1 GHz we found 1.35 V to be pretty stable.
At the bottom of the page you’ll see CPU Features, go into that menu. Here you can set your long duration power limit and CPU Current Limits. Maxing these out will stop your motherboard from downclocking (throttling) your CPU.
So with these settings we boot into Windows and see if our system can handle AIDA64’s system stability test (CPU test only).
As you can see the system is maxing out at 90C, which is not horrible for the i9-9900K. Keep in mind we are using an NZXT Kraken X52 for cooling.