CPU Speed dropped and won't go up.

Did you clean the fan? If the fan can't provide sufficient airflow the CPU might heat up and lock the speed to protect itsself.

Edit: Have you changed anything on the hardware side (like trying to overclock, change voltages, new/removed fan,...).

Uhm, had the same issue yesterday. For me it was the laptop charger that was faulty. You may want to try another charger to make sure, and for safety, if you can open the case, dust it off, and apply some new thermal paste.

l.e: After reading the extra info. Try performing a stress test on the CPU, from CPU-Z, does it pass the 55% usage in the stress test? If not, i'm betting the laptop battery/charger is faulty and cannot supply enough power to the CPU. Also, the CPU does not heat, because it does not get hot, since it does not pass the 55% usage, so the cooler speed does not increase.

Maybe you need to clean the insides of your PC, of dirt and other things such as hair.

Apply a new layer of thermal paste to your heatsink -- just a tiny dot in the middle before reseating heatsink

1. I have heard amd processors have a feature called Cool n quiet which lowers clock speed when there is minimal load. You may have turned it on.
2. Overheating can cause it, forcing the processor to slow down to vent extra heat and produce less heat until its at a decent temperature.

Sounds like heat throttling. Your laptop either needs a good dusting or a new cooling fan.

If You cleaned it, fan is clean, You changed thermal paste and etc. and its till like that
means You just damaged Your CPU. I have some for sale if You need XD

Check multipliers of your CPU in the BIOS, if they are reduced - max them out to heat 1400MHz (it happen to me once)

If it was me i would backup the things i want to save on another driver, them open it clean, format and see if the problem is still there.
The problem with pc's are they have some common problems that can be many diferent things.

My first idea - problem with cooling system. Try to force it to work at full speed by disabling all quiet, silent or similar functions in BIOS/Catalyst. If it won't speed up try cleaning fan and checking if thermal paste is applied correctly.

It also could mean that fan is damaged, and you will have to replace it.

Problem solved. Windows changed some settings to make battery usage limit the CPU speed.