Question i9-9900K doesn't seem to be hitting 5GHz boost clock


Dec 3, 2010
I recently bought a GIGABYTE Z390 AORUS PRO WIFI LGA 1151 motherboard and a Intel Core i9-9900K Coffee Lake 8-Core, 16-Thread, 3.6 GHz (5.0 GHz Turbo) cpu. Everything is working fine, but I noticed that compared to the i5 -6600K I had before the i9-9900K never hits the listed turbo speed of 5.0GHz.

The i5 -6600K would hit the turbo speed of 3.90 GHz if I ran the AIDA64 System Stability Test or Prime 95, but the i9-9900K never goes higher than 4.7Ghz. Even on a CINEBENCH single core CPU benchmark it never gets higher than 4.8GHz. I'm wondering if this this due to a setting on the BIOS of the motherboard or if the Turbo Boost of the i9-9900K is working as intended. I read online that max turbo with all cores active is 4700GHz, its just odd that even the single core test in CINEBENCH wont boost higher than 4.8GHz.


  1. 5,000 MHz
  2. 5,000 MHz
  3. 4,900 MHz
  4. 4,800 MHz
  5. 4,800 MHz
  6. 4,700 MHz
  7. 4,700 MHz
  8. 4,700 MHz
That's cores run at turbo speeds, so unless you run a 1-2 core stress, you'll always hit 4.7GHz as stress tests use maximum available cores.

With single core stress, the boost is tempered by both voltages and temps, so will throttle down the max boost if either exceeds it's predetermined limits. This can be reflected on the mobo VRM's, the cpu cooler, airflow, bios vcore settings etc.
Jan 9, 2020
As a 9900k owner who has tested a ton of stuff i can tell you this. all core turbo is 4.7Ghz and 4.8Ghz on single core turbo.The 5Ghz max frequency that intel mentions is the turbo boost power time window(as they call it) which means that the cpu boosts at 5Ghz for a specific time(28seconds when stock) if thermally capable to do so