Hi, I have an Asus X512Da laptop. and its processor frequency is stuck below. I think it is a bios problem because the battery is not charging. This has happened to me in past also. I had my motherboard replace at that time. but now this problem has reappeared in the new motherboard also. I believe this happened after the bios update.
One thing I have noticed is that when I plug out my charger the CPU starts to work fine again. But I am sure this is not the problem with the charger or the battery. I have tried using different chargers also. this is not also a thermal problem.
I strongly believe the problem is with the bios.