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The original was posted on /r/buildapc by /u/union_of_hobgoblins on 2023-08-19 19:08:24+00:00.

I recently upgraded my CPU and GPU from a R5 3600/RTX 2060 to R7 5700X/RX 6750XT. My mobo is ASUS TUF B550, with one PCIE 4.0 slot and one PCIE 3.0 slot. I did all the necessary stuff before the upgrade, did my CPU first and updated BIOS and chipset, then DDUd before switching GPUs.

I initially plugged my GPU into the 4.0 slot, which caused my PC to just power cycle and not post. After checking all cables and clearing CMOS, I switched the card to the 3.0 slot, at which point the PC posted and showed normal behaviour.

I initially assumed my first PCIE slot was malfunctioning, but just to be sure, I went to my BIOS and manually set the first PCIE slot from auto to 3.0 from, and then replugged the GPU into that slot, at which point the PC posted normally. After a few tests, this is what I found: PCIE set to auto/4.0 in BIOS - posts with RTX 2060, no post with RX 7650XT PCIE set to 3.0 in BIOS - posts with both cards.

Is there some incompatibility between the RX 6750XT and PCIE 4.0 that I am not aware of? Just wondering if anyone else has faced a similar issue. All of my drivers are fully up to date.