There are only two reasons these low frequency caps happen most of the time, especially on relatively new systems, and that is
1. CPU is "actually screwed". Which is REALLY uncommon.
Or,
2. Motherboard is fracked. And that is NOT uncommon.
I'd suggest that you list your FULL hardware specs, EVERY SINGLE thing you've already tried AND ANY other relevant information that you've not already offered.
I mean, there are other reasons why this can happen, especially if it's a laptop, but it's still not specifically "common" without some other conditions being met.
Its a PC. It all started when I changed hardware,getting a new GPU. I made the mistake of forgetting to uninstall the drivers first and got driver signature BSODs. I now realize if I had gone back to my original configuration,it probably have booted but I was too frustrated to think straight so I instead did a clean install of Windows 11. At first it went well but then I got Winload.efi BSODs and sometimes NTOS.Krnl ones,which I now realize was caused by Secureboot being enabled,but that's never been a problem before. After a few more install attempts of windows later,I noticed it being very very slow in everything and this was before disabling secureboot as sometimes it would load windows,albeit slowly and I managed to install some updated only to lead to the winload.efi crashes. I also changed to a different install drive as I was thinking the one I was installing on may have had issues. I also soon noticed that in BIOS,it was saying 520MHz as the frequency even though it was set to defaults of 3500 base. But now it reads what I set it to with Ryzen Master,although it still goes very slow so it must be reading it wrong. My motherboard and CPU are only a year old or so. I never overclocked,other than using PBO and now every time I (slowly) boot windows,I have to make my way into Ryzen Master and disable prochot,which from what I understand disables thermal limits for extreme overclocking. I find it hard to believe installing windows 11 a bunch of times could have messed things up,much less installing a new GPU. I do not understand why its doing this.
As for my specs:
Ryzen 9 3950X w/ NH-D15
MSI B550 Gaming Edge Wifi motherboard with latest BIOS from MSI
32GB G.Skill Aesir
Radeon RX 6750XT (was RX Vega 64 with a RX 580 for mining)
Windows 11 on Samsung 970 Evo Plus 1TB NVME
Cooler Master HAF XB Evo with plenty of fans
Other storage:
1TB WD Blue HDD
2TB WD Blue 2.5" SSD
512GB Plextor 2.5" SSD (was the OS drive before)
I feel its most likely a pure BIOS issue but I flashed it with a new version and it didn't help. The only physical changes made were the new GPU and then multiple attempts to install Windows 11 after that. IS there anything else you need to know,I cannot think of much more but maybe if you can,I can answer.
EDIT:Also,one time BIOS failed to load right and did it partially in Japanese for some weird reason and after I disable prochot,it runs exactly as it used to. Set to 3.98 GHz,which used to be what it more or less boosted all cores to with PBO enabled and voltage is set to auto so stays in the 1.2V range,near as I can tell. Still gets the 20K in Cinebench R15 it always did and only gets up to about 81C while running that test,as it always did. If there is a way to disable prochot in BIOS or have some other work around,it should be okay...I hope.