Hi,
Sounds like a BIOS problem, seems that it needs an update to support the new proc. Install the 2600, do a BIOS update, reinstall the 3700, and most likely it will work fine
🙂Greetz
AMD 5900X
Asus Crosshair VIII Dark Hero
64GB G. Skill 3600Mhz C16
Cooler Master Master Liquid PL360 Flux
Be Quiet Dark Power 12 Pro 1500Watt
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1 x Asus Strix RTX 3080Ti OC
CoolerMaster C700M
Samsung G7 Odyssey 32inch