The mystery of the slow CPU

Published on February 12th, 2009 at 6:38 am

Last modified on August 14th, 2012 at 12:04 am

Your laptop computer is rated to run at 2 GHz, but the information in the Control Panel’s System applet shows the CPU running at 900 MHz. What might explain this discrepancy?

A) The laptop was falsely advertised as a 2GHz processor but actually has a 900 MHz processor.

B) The laptop is saving power and minimizing heat by slowing down the processor when it’s not under a heavy load.

C) The System Information screen is displaying the incorrect processor speed because of a well-known Windows bug.

D) The CPU uses a multiplier to reach 2 GHz, but the System applet only shows the CPU speed prior to calculating the multiplier.

Answer: B) The laptop is saving power and minimizing heat by slowing down the processor when it’s not under a heavy load.

On laptops and other portable devices, the longevity of the battery is an important consideration. To maximize the time between recharging, manufacturers have implemented specialized hardware and software that are specifically designed to use as little power as possible to get the job done.

It’s also important to keep the temperatures inside of portable devices at reasonable temperatures. The CPU and associated processors are some of the hottest components of any mobile device.

If you’ve never experienced Intel’s SpeedStep or AMD’s PowerNow! technology before, it’s very confusing to see a slower processor speed listed in the Control Panel when you know the CPU speed is actually much faster. Laptop systems are a balance between speed, power, and temperature, and these speed throttling technologies ensure that the CPU isn’t using more power or creating more heat than necessary. While the system is idle, the CPU runs slower (sometimes much slower) than the maximum speed. When more processing power is needed, the CPU automatically switches to a higher clock speed.

All of this throttling is done automatically, and there are very few configuration options available for tuning. In most cases, the only options are to enable or disable the throttling. Be careful; if the throttling is disabled, the CPU will only run at the lowest processor speed. If you’re not sure of the setting, you may want to double-check the BIOS setting to confirm you’re getting the fastest possible processor speed.

Want to learn more? Watch “Laptop and Portable Technologies”


Although laptop and portable devices often provide similar functionality to desktop PCs, there are some important differences to consider for the CompTIA A+ exam requirements. In this video we’ll discuss some of these differences such as form factors, expansion slots, input devices, and power.

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Category: CompTIA A+ Pop Quizzes

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