It seems that anyone who installs an Ampere GPU starts having an annoyingly loud and rapid 4-beep BIOS code when UEFI with CSM or Legacy BIOS is enabled, this is normal. It's not indicative of an issue with your mobo or GPU. It is an annoyance related to Ampere and not a mainboard or GPU defect. It does not affect functionality.
Beeps with 3090 FTW | EVGA ForumsPlacing a piece of electrical tape over the hole in the motherboard's speaker dramatically reduced the magnitude of the beeping. It is still audible, but very faint and no longer annoying. I multi-boot Windows 7, 10 and Linux, so having Legacy BIOS or UEFI with CSM enabled is an absolute must. I do not use a pure UEFI setup for anything.
Wraith // Z790 Apex | 14900KF | 4090 Suprim X+Byksi Block | 48GB DDR5-8600 | Toughpower GF3 1650W | MO-RA3 360 | Hailea HC-500A || O11D XL EVO
Banshee // Z790 Apex Encore | 13900KS | 4090 Gaming OC+Alphacool Block | 48GB DDR5-8600 | RM1200x SHIFT | XT45 1080 Nova || Dark Base Pro 901
Spectre // Z790i Edge | 14900KF | 3090 Ti FTW3 | 48GB DDR5-8200 | RM1000e | EK Nucleus CR360 Direct Die || Prime A21
Methuselah // X79 Rampage IV Gene | Xeon E5 1680V2 | Titan | 32GB DDR3-2400 | GameMax 850W | EK Nucleus CR360 Dark || Prime AP201
Half-Breed // Dell Precision 7720 | BGA CPU Filth+MXM Quadro P5000 | 4K Display | Sub-$500 Grade A Refurb | Nothing to Write Home About