I replaced my Gigabyte AORUS Pro Z390 motherboard with an ASUS ROG Maximus XI Hero, leaving all other hardware unchanged. The system posts normally, but the i9-9900K temperature keeps climbing while sitting in BIOS, reaching around 90°C with only about 4% reported usage. I have shut it down to avoid damage.
I reseated the CPU and reapplied thermal paste, but the behavior remains. The cooler is an NZXT Kraken X53; its radiator fans spin, the USB and SATA power connections are plugged in, and I have tried connecting the three-pin cable to both CPU_FAN and AIO_PUMP. The BIOS reports roughly 3,000–4,000 RPM, although I am unsure whether that confirms the pump is actually moving coolant. I heard some gurgling during the first boot, but it has stopped. Could the pump have failed, could there be trapped air, or could the new motherboard be applying unusually aggressive CPU settings?
2 Answers
The ASUS board may be applying aggressive automatic voltage or boost settings out of the box. Check the CPU voltage, load-line calibration, and any multicore enhancement settings, then load optimized defaults or update the BIOS before judging the temperatures. A firmware update may also improve the board's automatic settings for the 9900K.
The reported fan or pump RPM does not always prove that coolant is circulating. With the system running briefly, listen for the pump and feel both tubes near the block. You should normally feel a slight vibration and eventually a temperature difference between the tubes. If there is no movement or one tube stays completely cold while the CPU rapidly overheats, the pump could be blocked, airlocked, or failing. Also confirm that the pump is receiving SATA power and that the radiator is positioned so a large air pocket cannot sit in the pump housing.
I have not updated the BIOS yet because I need another computer to prepare the USB drive. I will check the automatic voltage settings as well.