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Sometimes, through no fault of our own, we may lose the charging cable for our laptop and have to make do with a “less than optimal” substitute. If the “replacement” charging cable is from the same company, but is a different wattage, can it cause the laptop to slow down? Today’s SuperUser Q&A post has the answer to a curious reader’s question.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Photo courtesy of alistairas (Flickr).

The Question

SuperUser reader user3172050 wants to know if using the wrong power supply can slow their laptop down:

I have a Dell Studio XPS 1640 laptop and it requires a 90-watt charger for use. I lost my power cable, so now I am using a 65-watt charger with it. My laptop experiences a noticeable slow-down whenever it is charging, but everything speeds back up as soon as I unplug the cord and charger. Could this be because of the 65-watt power cable itself?

Can using the wrong power supply slow a laptop down?

The Answer

SuperUser contributor Maxx Daymon has the answer for us:

Many Dell laptops are able to use 65, 90, and 130-watt power supplies, but they will adjust their performance accordingly. Dell Support article 12174 (KB 168345) notes:

  • The Dell Universal Auto/Air Laptop Adapter is a 65-watt power adapter. Dell recommends that you use a 90-watt adapter with your portable system. Using a 65-watt power adapter will not harm your system, but will cause slower performance.

Specific performance throttling will vary depending on your CPU, chipset, and GPU, but overall every component will be slowed down to afford enough power to charge the battery and operate the laptop simultaneously. Laptops that require more than the 65-watt minimum (Precision workstation class laptops, for example) will simply refuse to charge when a 65-watt adapter is plugged in.


Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.