My new 9900k will not start into Windows on 8 cores, the 9600k in that board worked fine. If I only enable 6 cores on the 9900k it starts fine. even with 7 it freezes during startup. Getting into BIOS is not problem. Latest BIOS is installed

[AlHill]

Windows 7 is not supported. Only windows 10 is supported on 7th gen and later processors.

Have you updated the bios on your motherboard?

Doc

[LHans3]

Hello,

yes, its the latest BIOS and I run win10 pro 64 bit

[AlHill]

Are you certain your motherboard and bios supports the 9900K? What is the motherboard model number?

Doc

[LHans3]

Yes, it's the AORUS Z390 I pro wifi

[AlHill]

Well, either gigabyte support or one of the Intel support engineers will have to assist you.

Doc

[LHans3]

I will get another Z390 board in the next days, will check and confirm the CPU or the board is the issue ( But I tend to believe its the CPU, it was starting once with 8 cores, then crashed in Windows and never started again on all cores

[n_scott_pearson]

Have you tried reinstalling Windows?