Windows Prefetcher tips and info

[PseudoRandomDragon]

The Windows Prefetcher Guide

One of the hidden features in Windows XP (only) is the prefetcher. It, quite simply, works to speed up the launch of applications by loading them before you access them. It primarily works by loading startup programs during the time windows is still booting so that when you enter your password, everything loads quickly. It also keeps a record of all programs launched and how much they are used to aid in allocating how much prefetching to which program.

Contrary to popular belief, it is not responsible for making windows boot as fast as it does. In fact, the prefetcher only makes that it longer, since with the prefetcher activated it uses that period of time to load the other stuff that's going to load. But this is still a good thing, as it is annoying to continue waiting for stuff to load after you enter your password. The prefetcher works to take all the loading to the windows boot logo stage to make everything else that requires your interaction faster.

The prefetcher has a file for each program that you run that, in part, records the amount of use. Logically, programs that are loaded often are prefetched more than programs that are not.

The prefetch files are located in %windir%\prefetch. That's C:\windows\prefetch for those who don't know. If you opened it now you would see a whole bunch of .pf files and one layout.ini file. All the .pf files are individual recoards of each program. The layout.ini file is a consolidation of all those programs and what they typically access, in order of priority.

The prefetcher requires scheduled tasks to work. If you have the service disabled or off, the prefetcher will not function.

Tweaking

Your prefetch folder is probably full of programs that you don't even have installed anymore, or only used once. If you want you can always delete everything in the folder. Doing so has no bad effects on the system except you will notice that the computer loads differently on reboot. After you delete everything, the prefetcher will start the process again from scratch.

You can tell the prefetcher if you want to monitor boot files, monitor applications, monitor both, or nothing, by either editing the registry. There are also programs that provide a user interface if editing the registry scares you.

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

For "enableprefetcher", 0=disabled;1=monitor application launch;2=monitor boot files;3=monitor both (default)

Note that there is no other value that will do anything other than 0-3. Higher numbers probably just turn it off.

Now lets say you want to have only certain applications prefetched. You can do this by setting the prefetcher to only monitor boot files and setting a special switch in the program shortcut: /prefetch:1 . This doesn't work for all programs, but it does work for firefox so I'll use that as my example. Right click the firefox shortcut, select properties, in the target box insert /prefetch:1 at the end. Alternatively you can set certain programs to not prefetch by adding /prefetch:0 .

[Hypoxiaicon]

Damn handy tip!

I know where the Prefetch is, but for people who dont maybe add the URL for it?

[Zxian]

Good info.

Just a note. Certain programs won't accept the /prefetch:1 switch (such as Outlook). They'll take it as an actual switch and try to process it.

I'd also recommend completely turning off the prefetcher for systems with 128MB or possibly even 256MB of RAM. The more data that's being prefetched, the more memory that's being used up, and on low memory systems, it takes its toll.

[PseudoRandomDragon]

The prefetch files are located in %windir%\prefetch. That's C:\windows\prefetch for those who don't know.

[PseudoRandomDragon]

Just a note. Certain programs won't accept the /prefetch:1 switch (such as Outlook). They'll take it as an actual switch and try to process it.

This doesn't work for all programs, but it does work for firefox so I'll use that as my example.

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[McLaren_F1]

You Could also download Windows XP Prefetch Clean And Control and use that.

[devyant]

Excellent tip, thanks :)

[.AlleymaN]

guys..this prefetch thing is a myth..u ppl shud look at this

[PseudoRandomDragon]

The guy makes good points and adds to knowledge about how the prefetcher works.

Clearing out the prefetch folder every week doesn't increase performance. Heh, if you did that then you might as well turn it off.

I'm not sure about what he wrote with the /prefetch:# switch, but the proof is in the firefox quite frankly, as with that switch firefox loads in one second as opposed to about 15 seconds (but has the down side of increasing the time it takes to boot).

[+Warwagon MVC]

ya I have prefetch turned off and my computer feels like it preforms better because of it, if not for the startup BOOST!

[IceDogg]

ya I have prefetch turned off and my computer feels like it preforms better because of it, if not for the startup BOOST!

586136347[/snapback]

how do you turn it off completely?

[+Warwagon MVC]

dont' quote me on this ..bu I think its under hkey local machine/system/current control set/control/session manager/memory managment/prefetchparameters and change the enableprefetcher to 0

Edited June 29, 2005 by warwagon

[IceDogg]

dont' quote me on this ..bu I think its under hkey local machine/system/current control set/control/session manager/memory managment/prefetchparameters and change the enableprefetcher to 0

586136441[/snapback]

holy.. geez, that's deep in the registry. Thanks

[+Warwagon MVC]

holy.. geez, that's deep in the registry. Thanks

586138122[/snapback]

did you get better system performence after turning it off?

[PseudoRandomDragon]

how do you turn it off completely?

586136415[/snapback]

-_-"

Warwagon, IceDog, you are embarassing yourselves. The questions you asked can be answered right in the post I made.

[+Warwagon MVC]

gotta do that every once in a while

[IceDogg]

-_-"

Warwagon, IceDog, you are embarassing yourselves. The questions you asked can be answered right in the post I made.

586138975[/snapback]

yea I seen that after I posted my thanks.. DOH.. sorry bout that. I don't know how I missed it before. I did read your post though. :blush:

[PseudoRandomDragon]

That's ok, everyone makes mistakes.