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Home > News > Microsoft > Tips & Tricks

February 12th, 2007, 16:21 GMT · By Dragos Jijau

Speed Up XP with Prefetch Settings

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The birth of Windows represented a reference point in the computer history. For the first time, users have been able to work with more applications at the same time, using the new improved system based on the windows - application symbioses. The MS-DOS was immediately rejected and everyone adopted the new operating system with visual interface.

Nowadays, Windows reached a high standard using improved techniques to optimize the application handling. More and more programs are run every day on our computer and the hunger for new applications with exciting features is getting higher and higher. A large number of programs means using a lot of resources.

In order to optimize the applications running process Microsoft developers implemented a method to speed it up using a prefetch folder. The purpose of this folder is to collect and store information regarding the installed applications and later use it to speed up loading programs.

Windows XP is configured to copy parts of applications and later, when users start the application again, it will load faster because Windows has data already available. All the data prefetched will be stored inside the prefetch folder.

The bad part
is that Windows prefetches all kind of applications even those you seldom use and this will do exactly the contrary of the main purpose. Too much prefetched data inside the prefeched folder will slow down the system.

To obtain maximum performances I recommend you to periodically check the folder and empty it in order to get rid of unwanted data located inside, which eats up space and memory with a negative implication over the system performance.

To take a look inside the folder follow this path:%systemroot%prefetch. Usually, the system root is c:Windows. Just replace %systemroot% with the correct location of your Windows folder.

Once you got inside the folder, you will be amazed to see how much content you will find. The files inside use the name of the application, some data attached and the .pf extension. Moreover, to see how old some files are, just select the detail view in windows explorer and click the date to sort the files according to the creation date.

You have the possibility to delete all the files inside or just to select the ones linked to applications that you do not use anymore. What you delete is up to you. Deleting all the files is safe, don't worry. It won't affect in any way the proper run of any application. However, do not empty the folder every day, because Windows will keep prefetching applications every time.

Setup the prefetch folder

As I mentioned in the first part of the article, Windows is trained to use the prefetch method. You can tweak the settings in order to obtain what suits you best. The settings are not available under any shortcut or options menu. You need to do a rough job editing the registry yourself.

Go to Start > Run and type Regedit. It will open the Registry Editor. Using the Editor go to this location:

HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>Control>SessionManager>Memory Management>PrefetchParameters

On the right, there is a string called EnablePrefetcher. Double click on it and you will notice that the value data is set to 3. You can change this value according to the value significances and to your need:

0 - Disables the prefetch

1 - Prefetches only the application launch

2 - Prefetch the Boot

3 - Prefetch everything
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READER COMMENTS:


Comment #1 by: Larry Miller on 20 Nov 2008, 21:07 UTC reply to this comment

This article is quite confused and contains more than a few errors. The advice presentd will not improve performance but will impair it. It is based on a complete misunderstanding of how prefetch works.

Prefetch files are used to optimize both boot and application launch times. It is important to understand that application prefetch files are referenced only when the application is launched. They are not referenced in any way at boot time. The information is obtained from previous launches and enables Windows to load the application more efficiently.

Unused or rarely used prefetch files will have virtually NO impact on performance, even if in large numbers. In any event the prefetch folder is self cleaning after 128 entries. Manual deletion of these files will deprive Windows of a valuable resource and has no benefits. All of this has been extensively tested.

The prefetch system requires that the Task Scheduler service be enabled and set to Automatic. Otherwize Windows will be unable to add to, update, or delete any file in the prefetch folder. Over time this will lead to impaired performance.

The default and optimum value for the EnablePrefetcher registry entry is 3. There is nothing to be gained by changing this value.

References:
http://home.comcast.net/~SupportCD/XPMyths.html
http://www.edbott.com/weblog/archives/000024.html
http://blogs.msdn.com/ryanmy/archive/2005/05/25/421882.aspx

Larry Miller
Microsoft MCSA


Comment #2 by: James Marks on 20 Sep 2009, 15:33 UTC reply to this comment

If prefetch automatically empties its contents after 128 entries there is no need to change its settings in the registry that runs contrary to speeding up system performance.

A fallacy I have read many times in other articles too. Thanks Larry for clearing up this widely accepted misconception.


Comment #3 by: Brian on 11 Mar 2010, 08:19 UTC reply to this comment

Would someone please explain why you guys don't ID your selfs? Like are you the hacker who likes to have prefetch on for some reason? we the public don't know who is giving this info so why does Microsoft have and entry 0,1,2,3 if there is no purpose in it?????? Which add agency do you work for so all your adds can get prefetched?

Comment #3.1 by: Togi on 02 Aug 2011, 10:02 GMT

you also don't introduce yourself.. why should we ;


Comment #4 by: jack on 09 Apr 2010, 01:40 UTC reply to this comment

clear the prefetch files. virus's that are installed in your computer well get a prefetch file. run your autivirus program to clear the virus, then clear the prefetch folder. Windows will automaticlly put the prefetch files back.


Comment #5 by: Doc on 15 Jan 2012, 15:22 UTC reply to this comment

It's surprising that a few people would be saying that a general practice recommended by dozens of qualified tech support groups for improving performance are wrong, the prefetch folder isn't merely a reference, it is what tells the computer what files to preload into memory both system and paging, in case of need. As a result, less memory is available for running applications, which can cause a significant decrease in performance.
It's a trade off, faster loading time for multitasking different applications with slightly lower overall performance, versus superior performance when running one application at a time at the price of a slightly slower loading time.
For Office work it's likely best to leave the prefetch setting at it's default 3 (Prefetch Everything), but for gaming it's better to set the prefetch to 2 (Boot Prefetch) or 0 (Disable Prefetch)


Comment #6 by: sd on 01 Aug 2012, 02:40 UTC reply to this comment

if i delete Prefetch Folder. then system any problem

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