Windows XP / Beginners

The registry to optimize the Prefetcher

Located inside the System Registry are the settings for the Prefetcher component of Windows XP. Several different settings can be changed, such as the mode that the Prefetcher is running in, the number of items that are tracked by the Prefetcher, and where the Prefetcher cache is located. Several more can be manipulated.

Almost all of these settings are not published in documentation available to the public. The only setting that Microsoft has said anything about is the EnablePrefetcher setting. Some users of Windows XP were having trouble with the Prefetcher, which caused problems with certain unknown applications, so Microsoft released information on how to disable the Prefetcher. Also, around the same time, information became available on how to disable or enable certain parts of the Prefetcher.

The Prefetcher can be either disabled or set to optimize the boot only, to optimize applications only, or to optimize both applications and the boot. By default, the Prefetcher is set to optimize both. This default mode sounds like it is the best one for all users, but some people have discovered better performance by experimenting with the different modes.To change the modes of the Prefetcher, follow these steps:

  1. Start the Registry Editor by clicking the Start Menu and then selecting Run. In the text box, type regedit, then click the OK button.
  2. This will load the Registry Editor. Once it has loaded, expand HKEY_LOCAL_MACHINE.
  3. Expand SYSTEM.
  4. Expand ControlSet001.
  5. Expand Control next.
  6. Now you will see Session Manager. Expand that as well.
  7. Because you will be changing the setting for memory, expand Memory Management.
  8. Finally, open PrefetchParameters and you will see all of the Prefetcher settings.
  9. Locate the EnablePrefetcher doubleword value and right-click it and select Modify.
  10. Once the Edit DWORD Value box is shown, update the number with the corresponding number.Which number you use depends on how you want the Prefetcher to act.
    Refer to Table in next section for all of the options and their meanings for this value.
  11. Click the OK button after you have updated the value and restart your computer.

Experiment with these different settings on your computer to see which ones work best for you. The prefetch information used by this mode is also used in other parts of the operating system to improve speed. For example, it is used by the boot defrag.

Feel free to experiment with other settings, such as AppLaunchMaxNumPages, AppLaunchMaxNumSections, BootMaxNumPages, and BootMaxNumSections. The other settings alone because they are all in hexadecimal format, which can be difficult to work with. But make sure that before you do any tampering, you use system restore to create a restore point so that any problems that you may cause can be easily undone.

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