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Just another software developer with opinions

Dell Laptops Throttle On Non-OEM Adapters

A good thing to know before buying Dell hardware

Nov 29, 2019 · 3 min read

For this season's tech support exercise, I was debugging why my parents' laptop would randomly become slow to the point of useless. It all started this morning when I was told that the machine wasn't charging despite being plugged in. Clicking on the battery icon, Windows would show:

Plugged In. Not charging.

It wasn't surprising at first, since the battery level was well above 90%. I know that some devices have regulated charging, where it would vary the rate of charging to preserve battery life. Some devices would charge regularly until around 90%, then slowing down to reach 100%. But a few internet searches say it wasn't the case.

One of the solutions mentioned reinstalling the adapter driver, possibly because it's out of date or malfunctioning. Simply uninstall, reboot, and Windows would reinstall it automatically (Fun fact: Windows comes with generic drivers and pulls from Windows Update if it needs to). So, I tried the proposed fix.

No dice.

However, I noticed something odd. The machine was unusually slow. I very well know that a Pentium-class processor isn't the fastest in the world, but it's just very unresponsive. Opening apps took forever, interactions were janky and juddery. So I checked task manager if a process is hogging the CPU. And then I saw...

CPU usage: 30%

That's odd. It wasn't because it's only using 30%, it's being capped at 30%, no matter what load I put on it. I initially thought it was the power plan or the performance/battery slider holding it back. Nope. Some even suggest it's the Intel power plan driver malfunctioning, but it wasn't that either. And I just recently replaced the batteries so it can't be that.

Through a mashup of different keywords, I finally stumbled across something interesting. Dell boards would throttle CPUs when a non-OEM adapter is plugged in. It does this by sending an "overheat" signal to the CPU when it detects a non-OEM adapter. The CPU, thinking it's overheating, would throttle and become slow.

The official reason for this feature was hardware safety. When the adapter used isn't an OEM adapter, the board doesn't know how much power it can pull from it safely. And so, the laptop throttles the CPU to avoid overloading the adapter as well as prevent the system crashing due to insufficient power. It also stops charging the batteries.

But others see this as a vendor lock-in mechanism. Unless you're going to buy an OEM adapter, the board will continue to reject your adapter, throttle your CPU, and not charge your batteries. You must get an OEM adapter to avoid these problems. And, as we all know, vendor-specific hardware can be quite expensive.

Conclusion

I still don't know which part of the charging circuitry is broken. It could be the adapter, the barrel, the socket, or the charging circuitry in the laptop that's to blame. Sometimes the laptop does detect the adapter, sometimes it doesn't. Loose cabling maybe? I don't know.

But at least I know now that Dell laptops and adapters work this way. I was considering getting an XPS laptop for work, but kept putting it off. Now that I know Dell hardware works this way, they're no different from Sony and Apple - two companies I despise for their vendor lock-in and anti-repair practices.

I guess I'm now staying away from Dell hardware too. 🤔

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