Dell Laptop Stuck at 800 MHz CPU Speed — Charger Fix and ThrottleStop

The first time I ran into this, I was very surprised. Why is the laptop so slow? It felt like an ancient computer.

I looked in Task Manager and saw that the CPU was running at 800 MHz!

The funny part: when I unplugged the charger, the frequency went back to 2100 MHz and the laptop came alive. Plug the charger in, and it’s 800 MHz again.

After reading a pile of forums and discussions, I understood that the charger was the cause.

Modern power adapters for Dell laptops (and not only Dell) have a special chip that lets the BIOS tell whether a “correct” charger is connected.

So if you plug in an adapter from a different model (a less powerful one, with a matching voltage and connector), the laptop switches to a special mode with a reduced CPU frequency.

In that case, people had mixed up the chargers and used the one from a 15″ model. It was a 60 W adapter instead of 90 W. After the chargers were swapped, the 17″ laptop came back to life and ran normally. The 15″ model worked fine with the more powerful charger, so the swap didn’t affect it.

Later I came across another case: the power jack inside the laptop was broken, and the center pin of the charger didn’t reach the contact, so replacing the charger didn’t help. The laptop kept refusing to recognize its own chargers. The fix was simple: I inserted a bent piece of copper wire into the center hole of the jack, which restored the contact, and the laptop ran at full speed.

Some skilled people unsolder the chip from the charger and solder it inside the laptop, so that it works with any charger without these tricks. I wouldn’t do that. Extra tinkering inside a laptop is unnecessary.

I have seen the same problem on some HP laptops, but there it is even wilder: the frequency dropped to 400 MHz, 0.31 GHz, 0.48 GHz, or 0.7 GHz, again because of the power adapter.

There was also a case where the frequency dropped even with the original charger, and nothing helped. There is a way out in that case, too.

ThrottleStop

The free program ThrottleStop helps. Download it from TechPowerUp and run it.

In ThrottleStop, turn off the BD PROCHOT option and apply the setting. Note that this option disables overheat protection!

So you must check how hot the CPU gets under your load. You may need to clean the dust out or replace the thermal paste.

ThrottleStop has other settings for tuning, but that’s for enthusiasts. Finally, add ThrottleStop to startup with the highest privileges, with BD PROCHOT turned off, and you can work at full speed.