For some unexplained reason my TUF 4090 card only runs PCIE4 x8 in 9 out of 10 startups, and 1 out of 10 startups the card runs at PCIE4 x16. When the card boots in x16 speed it will remain that speed throughout the session until i reboot. After reboot, it most probably goes back to x8 speed. The card should always start in x16 speed, but it doesn't.
To clarify, the x8 does not change to x16 when putting the card under heavy load (benchmarks) or playing intensive games. The x8, or x16, will remain that speed throughout the session, until i reboot.
I have tried to find possible explanation to this but i can't. (e.g. if something is stealing PCI lane speed etc)
I have a prebuilt PC with below specs. I have tried every possible solution to the problem, updating bios on motherboard, updating vbios, played around with mobo bios settings like forcing x16 speed, disabling integrated gpu etc.
My motherboard should not share the PCI16_1 slot speed with anything if PCI16_2 slot is empty (which it is).
I have also tried to reinstall windows 11 four times, the problem persist exactly like above even before installing any drivers. And i have run the card in Eco mode and Performance mode, no difference in this behaviour.
As this is pre-built PC, should I send it back to the builder for review? Or is this a driver/bios problem (since i sometimes run the card at x16).
Thing is I have already sent the PC back once before (few weeks ago), where my previous problem was motherboard not detecting my vcard. For that problem they concluded that my motherboard was faulty, now i dont have this problem as they exchanged to a new x670e Hero motherboard. But this x8 problem persists, but not always!
When i emailed them that the x8 is not fixed they claim it ran x16 during their tests (which i do not blame, as i sometimes get x16 speed on bootup).
Any suggestion on what i should do?
Mobo: ASUS x670e Hero (bios 0805, tried 0705 before that)
GPU: ASUS TUF 4090 24 gb (non-oc) - latest v.2.1. vbios. (had the v2 bios before)
CPU: AMD 7900x (stock)
RAM: Kingston Fury Beast RGB 5600 2x16gb
PSU: Corsair RM1000e 1000w
SSD: Kingston FURY Renegade PCIe M.2 NVME SSD 2TB. PCIe4
OS: Windows 11, latest version