Korea: 1-second freeze every ~minute, FPS halves, GPU util to 0, controls dead (7800X3D / 4090) — also in menus

[goewi]

Specs
CPU: AMD Ryzen 7 7800X3D
GPU: RTX 4090
Korea. IL-2 Series, current release build
What happens:
About once a minute the game freezes for ~1 second.
If I am running a smooth 120 FPS, it drops to 60 for that second, then returns to 120. Same pattern at other caps: FPS halves to the next floor, then recovers.
During that second:
The picture freezes
Controls do not respond (stick / mouse)
NVIDIA overlay shows GPU utilization drop to 0 briefly
After the second, everything returns to normal
I miss shots and lose control for that beat. It is short but it happens often enough to be a problem in combat.
This is not only in flight. It also happens in the menus.
Great Battles on the same PC does not do this.
What I already ruled out
Different FPS caps — the hitch still happens; only the number it falls to changes
Not a sustained GPU overload (utilization falls to 0, it does not peg at 99%)

 

Anyone else having this? Any ideas? 

[Husar]

@goewi Try change SMP in UEFI.

Edited September 2 by Husar

[goewi]

Found the issue in case anyone else has this. It's was my USB hub causing the stutter. It's gone now!