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I have a Dell Studios XPS 1640, and it requires a 90W charger for use. I lost my power cable, so I'm now using a 65W charger.

My computer has slowed down noticeably whenever it is charging. The computer speeds up directly after I unplug the cord.

Could this be because of the power cable itself?

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2 Answers 2

up vote 22 down vote accepted

Many Dell laptops are able to use 65, 90, and 130w power supplies, but they will adjust 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 simultaneously. Laptops that require more than 65w minimum (Precision workstation class laptops, for example) will simply refuse to charge when a 65w adapter is plugged in.

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Stated differently, the hardware is reducing its power state in order to operate with less than full power available to it. Many devices have a specific requirement for operation. Plug a 9V adapter into a 12V electronic keyboard, it won't power on at all! Laptops, however, are designed to accept varying levels of power, and operate at various power levels to provide a longer battery life. However, if consumption exceeds the battery charge rate, the hardware will immediate lose power when the battery's level is critical, because it couldn't maintain operation. –  phyrfox Mar 1 at 21:16

Sounds like a possible 'safe mode' operation or throttling because of improper hardware/power source.

It is likely.

I have even seen it go as far as to not charge the battery at all if the proper adapter isn't used.

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