Mar 252008

One of the features introduced in Windows XP is called Prefetch wherein Windows caches the boot files and the most recently used application files so as to make Booting the system faster and load the previously loaded applications faster for the simple reason its been cached.

Windows XP prefetch in my words is a “Good Bad & Ugly” all packed into one. While definite advantage is that the system boot time and previously accessed applications faster, the downside is that the feature can clog the cache in itself with those unused programs and you do not have to wait for Windows loading all those application files which you may not used this time (say used watched DVD on a DVD player software and this morning all you need is to check a few word files).

The files are cached in C:\Windows\prefetch folder. The files can be safely deleted but the downside is that the next system reboot will a bit more time that it used to as it hasn’t got anything in its cache and that it needs to cache them all over again and the subsequent reboots will be faster.

There is a Windows registry tweak that can help you control how Prefetch performs or even enable and disable Prefetch in Windows XP.

To control Prefetch,

1. Click Start – RUN, type “regedit”

2. Navigate to the following Regsitry key

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters]

\Session Manager
\Memory Management

3. In the right-pane, look for the key “EnablePrefetcher” edit and set one of the following values as you require:

0 – Disable Prefetch in Windows

1 – Prefetch only Application Lauunch files

2 – Prefetch only Boot files

3 – Prefetch all

Say, you don’t need Application caching then simply set the value to “2″ which will prefetch only Boot files.

4. Reboot the system for the changes to take effect.

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  3 Responses to “Registry Tweak to control Prefetch in Windows XP”

  1. The explanation of how prefetch workds is seriously in error. Prefetch does not preload applications at boot time. Prefetch files are used to optimize application loading. Unused prefetch entries will have virtually no impact on performance. In any event the folder is self cleaning after 128 entries. Manual cleaning of the folder has no benefits and will temporarily cripple boot and application load times. All of this has been extensively tested.

    The default and optimum value for EnablePrefetcher is 3. Changing this will not improve performace in any way.

    This prefetch myth has been spread by a great many uninformed websites. Doing so seriously undermines their credibility among knowledgable users.

    Also check the references on this page.

    Larry Miller
    Microsoft MCSA, Network+, A+

  2. Take some time and run your own tests. I did.
    Result: I have set the value to 2.

  3. I agree, Steve. It’s not a myth. Booting Windows XP Home is several seconds faster with the registry setting at “2″.

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