Your motherboard automatically increased your CPU's speed, which is the default setting.
Your motherboard automatically increased your CPU's speed, which is the default setting.
9900k runs at 4.7 with all cores active, 4.8 at 8 threads (about 16 cores), and 2 threads at 5.0.
Currently I'm tuning my motherboard for overclocking (MCE) on an i9 9900k. The results show Cinebench R20 performance closer to the stock level. Over the past two years, it ran at 5GHz across all cores, yet games still deliver similar frame rates. It's been running with multiple GPUs—2x GTX 1080 in SLI, a RTX 2080 Ti, RTX 3080, and now an RTX 3080 Ti. The 3080 seems to be the optimal choice, offering plenty of potential for future upgrades.
In a way, modern systems automatically increase your CPU's performance. The maker employs techniques like turbo boost, which essentially means the CPU runs at a higher speed than normal when conditions allow—temperature stays manageable and power supply is sufficient. As heat rises, performance will gradually decrease.
It’s not uncommon for the CPU to stay near 4.7-4.8 during idle. This can simply reflect its current workload or thermal state. Your machine’s behavior isn’t necessarily unusual.
Intel base clocks focus more on warranty than performance. My i9 9900k runs with XMP enabled on an Aorus Ultra z390, using Multi Core Enhancement by default. At idle, this appears as expected. This model was assembled in February 2019 and achieved a 5GHz boost on its first run at 1.272v. I also performed an overclock when it ran with two 1080i displays, but the boost faded once the RTX 2080 ti was added. The overclock works best at 1080p; since then it’s stayed around 1440p and 4K. Keeping the system cool is key—my setup uses a Noctua D-15 fan, which keeps things stable in the 60s.