CPU FAQ

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Why does my AMD CPU have the "wrong speed"?

AMD actual speeds
Athlon 64 4400+3200 MHz
Athlon 64 4000+2800 MHz
Athlon 64 3000+1800 MHz
Athlon XP 3000+2163 MHz
Athlon XP 2200+1800 MHz
Athlon XP 1800+1533 MHz
Athlon XP 1500+1333 MHz

AMD uses a "processor rating" (PR) in the model name of most of their processors. The table at right shows a few samples of the AMD processor name versus actual rated clock speed. AMD's PR does not represent the actual clock speed of their processor, and is usually much higher than the processor clock speed.

Why does AMD use the PR in their model number? AMD processors generally perform better than Intel ones if they are run at the same clock speed; AMD's PR is designed to indicate the equivalent level of performance you might expect compared to an Intel processor. Companies that sell AMD-based systems may use the PR number in their model numbers or sales materials rather than the actual megahertz speed of the system. Benchmarks with real applications generally show that the AMD PR ratings are relatively accurate when compared to Intel performance.

Why is my PCs clock speed (MHz) so low?

Notebook and other portable PCs are designed to run at the lowest possible speed in order to preserve battery power and to prevent overheating. Both Intel and AMD CPUs have power management features built into their processors. Intel calls its technology SpeedStep; AMD calls its version PowerNow. One result of these power and thermal management features is that the processor is often running much slower than the "advertised" speed. This may be due to several reasons:

  • The PC may have no work to do at the moment. To save power, the CPU will slow down or even stop until something happens that requires work, such as a keypress or an incoming network message.
  • The PC may be running on batteries. To conserve power, the system may run at less than maximum speed, even if there is plenty of work to do.
  • The PC may have reached a "thermal zone", exceeding a temperature that the system designers did not want to exceed. The system may reduce speed or even shut down in these cases.

Beginning with the Pentium 4, Intel has incorporated some of the thermal and power management features into their desktop processors, and AMD has followed suit. On desktop processors, the emphasis is usually on preventing overheating due to inadequate cooling, rather than saving power. Nonetheless, the technology is basically the same, and is controlled by the same Windows settings.

How do I get max speed when using AC power?

In Windows XP, go to Control Panel | Power Options, Power Schemes tab. Select the "Always On" or "Home/Office Desktop" power scheme. (Yes, even if you have a notebook!)

How do I set CPU speed with power management?

XP Power schemeACBattery
Always OnNoneNone
Home/Office DesktopNoneAdaptive
Portable/LaptopAdaptiveAdaptive
Minimal Power ManagementAdaptiveAdaptive
Maximize Battery LifeAdaptiveDegrade
PresentationAdaptiveDegrade

In Windows XP, almost all notebooks use XP's built-in power management setup. Settings can be changed through Control Panel | Power Options, Power Schemes tab. (Depending on your setup, you may need to click "Switch to classic view" in Control Panel to see the Power Options choice.) The table at right shows how the choice of power scheme affects processor speed.

When None is in effect, the CPU will always run at full speed unless it reaches a critical thermal zone (in plain terms, unless it's overheating). For the Adaptive mode, the system will run at a lower speed until Windows decides that the system workload justifies moving the CPU to a higher speed. This may be done in several steps; the exact decision will depend on the workload, the power scheme, and the type of CPU being used. In the Degrade mode, the processor will always run slower to conserve power, and may even be stopped totally when possible. This will reduce performance, obviously.

Older versions of Windows will usually require a vendor-supplied utility that provides power management functions. These will vary depending on the CPU type, but should offer options similar to the ones built into Windows XP described above.

I'm using "Always On", why is the PC still slow?

If you are not seeing the best CPU speed even though you selected the "Always On" power scheme, it's possible that the PC is overheating. Usually there are several thermal zone points; in the lower temperature zones, the system will reduce the clock speed to keep the system cool. It can be normal for some PCs, particularly notebooks, to reach the lower thermal zones during operation and have their speed throttled back. However, if the system becomes dangerously hot, Windows will shut down the system.

To troubleshoot overheating problems, check to make sure that dust or dirt isn't blocking the air intakes or heat sink on the processor. For notebook PCs, do not rest the notebook on your lap using a pillow or blanket; it will act as an insulator, block airflow around the unit, and prevent it from cooling properly. Instead, use a lap desk with a hard and flat top surface. Utilities such as Motherboard Monitor or Speedfan let you monitor the temperature of your CPU, which can tell you if the performance problem is heat-related.

Why is my CPU misidentified?

In cases such as the processor name, vendors often release new processors before they update their documentation on how to identify the processor. If you believe your processor is being misidentified, please post a note on our forums.