I just built my first PC using the i5 9600k. I regularly get the CLOCK_WATCHDOG_TIMEOUT stop code with no other information. Checking the event viewer shows in info dump error followed soon after by a kernel power error. Also, since updating my BIOS, my PC will only boot with 1 of my RAM modules, never 2. I've tested every slot on my motherboard and only the A1 and A2 slots are a problem. These two issues may be unrelated but, like I said, this is my first time building a fixing a PC. I've spoken to the manufacturer of my motherboard and they said it was either a processor issue or a bad motherboard. In order to rule out my processor, I ran the Intel Processor Diagnostic tool. It always passes the full functional test but always restarts roughly 90 minutes into the burn-in test. So before I contact the motherboard manufacturer again, I wanted to completely rule out my CPU.
CPU: i5 9600k 300 Series
GPU: ASUS Geforce GTX 1660 Ti 6GB
Motherboard: Gigabyte Z390 AORUS PRO
RAM: Corsair Vengeance LPX 16GB (2x8GB)
PSU: Corsair CX Series 550 Watt
SSD: Crucial P1 1TB
Heatsink: be quiet! BK008 Pure Rock Slim
This timeout is indicative of the memory bus locking up. Either there is an incompatibility with your memory, the slots are bad or your memory is bad. Try using different memory. Verify that the memory you try to use is actually listed as supported by the manufacturer of this motherboard.