Question i9900k unstable with stock turbo boost (no oc)

[fossi]

I'm asking for troubleshooting help, because I don't know how I should proceed with my build problem.

parts list:

• cpu: Intel Core i9-9900K
• mainboard: Gigabyte Z390 Aorus Pro
• psu: be quiet! Straight Power 11 1000W
• cooling: Enermax LiqTech II 280 (aio)
• ram: Corsair Vengeance RGB PRO 4x8GB DDR4 3600MHz
• ssd: Samsung SSD 970 EVO Plus 1TB, M.2
• vga: RTX 2080 (problem persists with and without gfx card)

Problem:

My i9-9900k runs unstable with stock settings (in bios optimized default settings / all auto / xmp profile 1 enabled).
Symptoms:

• on boot, keyboard/mouse are not/rarely detected (fast boot is disabled)
• in bios cpu frequency shows 4.7ghz (as expected with turbo boost) and 29°C core temp
• booting window (new install) from nvme ssd results in a bluescreen (certain files not found, etc.)

Attempts so far to diagnose or fix the problem:

• removed 3 of the 4 memory modules and swapped the remaining one - no improvement
• used another psu (750w) - no improvement
• When disabling turbo boost and setting all cores to the same frequency, I can get up to 4.3GHZ on all 8 cores stable.
• No keyboard/mouse problems, windows boots fine from nvme ssd, prime95 run fine on all cores @4.7ghz with core temp at ~70°C.
• going up to 8x4.4ghz (and setting vcore up from 1.2 to 1.3) still boots windows, but prime95 doesnt even start
• going up to 8x4.5ghz (and setting vcore up from 1.2 to 1.3): again USB problems (mouse/keyboard not detected, windows boot bluescreen)

Additional details
This is a new build, I have removed every thing else from the board (tried with and without gfx card) and even set up the board outside of the case.
Bios is updated to latest version (F10) and I already tried clearing cmos.

Any ideas what might cause my problems?

 

[fossi]

pic of the socket... some pins in the rightmost column look slightly different ...

 

[fossi]

replaced rams, mainboard, psu ... no improvement.

replaced CPU (some modell) - all fine now. so it seems I had a defective CPU that had serious problems with boost mode enabled