Slow boot; CPU stuck at 400MHz


Thread Starter
Feb 25, 2020
Acer Swift 3 SF315-41G-R6MP Laptop
CPU: AMD Ryzen 7 2700U (Base Clock: 2.2GHz, Max Boost Clock: Up to 3.8GHz)

A few hours ago I started my laptop. Normally it boots in less than one minute but now took more than five minutes to boot. Once I logged in the computer seemed real sluggish. I checked the Core Temp desktop gadget and was surprised to see that the CPU speed was at 400MHz. Normally it fluctuates between 1.5 and 3.0 GHZ.

I shut the computer off and restarted it. It again started really slowly and was stuck at 400MHz.

I started Firefox but it stayed at 400MHz. That was not normal.

I started Prime95 and started Torture. I watched the CPU speed and temps with Core Temp. Here is what I saw:
All 4 cores: 100%
CPU Speed: 400MHz
CPU Temp: 52C
I stopped Prime95 after a few minutes.

I started CPUZ. It confirmed the CPU speed of 400MHZ. It had recommended an update so I updated it to 1.92.2. I started CPUZ again. Suddenly the CPU speed jumped to over 3GHz. I also noticed that the CPU fan had started at the same time. It had been quiet until then.

I rebooted the computer again. It now booted normally with the CPU speed also normal. The CPU fan also started and stopped like it should.

Can anyone explain the computers strange behavior?

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