CPU or motherboard defect or simply wrong settings?

Good day,

I built my new gaming PC a few days ago. All components are working perfectly, except for the CPU. Since the first boot, the UEFI has been showing that the CPU is only running at a base clock speed of 800 MHz, instead of the manufacturer's specified 3500 MHz. I installed Windows anyway, hoping that installing drivers would solve the problem, but nothing has changed.

I've tested all other components, and they work perfectly. No matter what applications I run, the clock speed remains unchanged, and performance is accordingly low. Maybe I need to change some settings in the UEFI to achieve the desired performance, but I don't know much about overclocking and the like. I've also heard that newer Intel processors are having issues right now, and I might be affected.

Here are my components:

• CPU: Intel Core i5-13600K
• CPU cooler: Asus ROG Strix LC II 360
• Motherboard: Asus ROG Strix Z790-A Gaming WIFI
• RAM: XPG Lancer DDR5 6000MHz CL30
• PSU: Corsair RM850e
• Graphics card: Geforce RTX 2070 (from my old PC)
• Hard drive: Crucial P3 PCIe NVMe 4.0 1TB
• Case: Phanteks Eclipse G360a

Things I have already done:

• BIOS update to the latest version
• Chipset driver updated in Windows
• CPU removed, reinserted and thermal paste reapplied
• 2x 8-pin CPU cables checked

I've tried everything I can think of, but the problem persists. Perhaps one of you can help me. I would be very grateful.

Thank you,

Alberto