Ryzen 5800x system crashing into reboot while under gaming loads unless 2 cores are disabled
CPU: 5800x (Noctua D15 cooler) - Max temp 64 degrees under load
GPU: Radeon 6800xt (Sapphire Reference Model) - Max temp 78 degrees under load
PSU: Corsair RM850x (850 watt)
RAM: Corsair Vengeance LPX 3200mhz
MOBO: Gigabyte x570 Aorus Elite Wifi
Issue: My new build crashes when under gaming loads and the pc reboots itself (no BSOD). At first, i thought the problem was due to insufficient power so I swapped my 750w power supply with a brand new 850w power supply (that's 200 dollars I'm not getting back due to return policies). I've tried reinstalling chipset drivers, graphical drivers, disabling XMPs, disabling SAM, disabling boosting, and plugging my PC into the wall outlet directly (instead of into a surge protector). I have run windows memory diagnostic, as well as 1 pass of memtest86 (will do more overnight), and I have tried several bios revisions (only ones that support Zen 3).
All my temperatures in HWInfo and all seem perfectly fine even upon crashing.
The only thing has seemed to work is running the 5800x as a 6 core processor using the BIOS settings. This causes the system to become stable. I'm extremely confused as to why this works, but it does.
Do I just have a faulty 5800x and need to RMA? Has anyone else encountered this problem? I'm very confused.