I've seen a number of differing views on prefetch, and would like to offer
some more and different info on why you might want to clean pre-fetch. It
doesn't stay a constant size for all--it can get too full in the equations
of some boxes rapidly. I don't think you can hurt yourself deleting
pre-fetch--it's going to reconstitute, but you may improve boot or
performance. If one takes a look at a number of articles on Pre-fetch, you
will come away with the idea that cleaning it or resetting its parameters in
the registry may speed not only booting, but performance as well, and you
do not compromise opening a program--it will be reconstituted and you have
gained something in two significant areas--boot speed and PC performance.
Google on Pre-Fetch
http://tinyurl.com/65fyt
http://techrepublic.com.com/5100-6270_11-5165773.html and here's a
contrarian view to that:
http://www.bootdisk.com/bootlist/138.htm
Pre-fetch Delete Favorably Impacts Boot Time
http://www.theeldergeek.com/prefetch_parameters_-_altering.htm
http://www.komando.com/tips_show.asp?showID=6737
Mark Russonovitch's (Sysinternals) Take on Pre-Fetch
http://www.techsoup.org/forums/index.cfm?fuseaction=read&forum=2009&id=52366&cid=117&mid=179692
From Kelly's XP:
http://www.kellys-korner-xp.com/xp_p.htm
Prefetch
Prefetch is a new and very useful technique in Windows XP. However, after
using XP some time, the Prefetch directory can get full and have obsolete
links in the Prefetch catalog, which can slow down your computer
significantly.
The Prefetcher component in Windows XP is part of the Memory Manager, and
helps to shorten the amount of time it takes to start Windows and programs.
Windows XP "monitors" itself and notices which applications are launched
frequently. It gathers information about these applications and what they
access with the launch and stores this information in the prefetch folder.
It then uses this information to "optimize" access to these files so that
they launch faster.
Once every three days, by default, Windows XP will perform a partial
defragmentation and adjust the layout of the disk based upon current use.
The files to be moved are written in the file Layout.ini (found in the
Prefetch directory under the System Root directory).
Suggestion: Open C:\Windows\Prefetch and delete the obsolete files,
reboot. However, if you don't have a real good
reason to delete these files, just leave them be.
Let the system handle this folder.
If system performance is an issue:
XP automatically optimizes itself every three days, bootvis forces the
optimization to happen now rather than having to wait three days. Fast Boot
/Fast Resume Design: A performance trace visualization tool for use with
Windows XP systems.
Bootvis can be downloaded here. For more information click here.
Manage the Windows Prefetcher Service: Go to Start/Run/Regedit and
navigate to this key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory
Management\PrefetchParameters
Create a new DWORD value, or modify the existing value, called
"EnablePrefetcher" and set it according to
(0 = disabled, 1 = Application launch prefetching, 2 = Boot prefetching, 3 =
Both prefetching). To clear the Prefetcher cache, delete all the files in
the Prefetch sub-directory (e.g. "C:\Windows\Prefetch").
Prefetch Defined: This directory is used by the defrag utility to help
organize the files on your PC for more efficient
loading.
"I/O performance is strongly influenced by the layout of files on disk.
Files and directories that are heavily fragmented or dispersed across the
disk will hurt performance. While Windows XP will automatically reposition
some files to improve performance, this will generally be done infrequently
and will usually include only a small fraction of the files on the disk.
Therefore, it is a good idea to defragment the disk following an
installation.
Once every three days, by default, Windows XP will perform a partial
defragmentation and adjust the layout of the disk based upon current use.
The files to be moved are written in the file Layout.ini (found in the
Prefetch directory under the System Root directory)." Windows XP
Performance
Boot Prefetching
Windows XP speeds up system boot by observing the code and data needed each
time the system is booted and prefetching the necessary file contents early
in the boot process. This prefetching is not done until the third boot of
the system, when sufficient information is available to make the prefetching
most effective. The files observed during system boot will be used in the
disk layout process mentioned above. Additional information on the
prefetcher and the Windows XP boot process can be found at Fast Boot/Fast
Resume for the Windows Platform.
Application-Launch Prefetching
Windows XP also uses prefetching when launching applications. The files and
the contents of the files accessed by each new process are observed and
recorded. No prefetching can be done for the first launch of an application,
so first launches are often considerably slower than subsequent launches.
About 85% to 90% of the improvement is realized after just one launch of an
application, with the remaining speed improvement coming after the system
has had an opportunity to adjust the disk layout with information specific
to this application. Benchmarking on Windows XP.
hth,
Chad Harris
Don't bother, the file is constantly changing. In 3 ½ years with XP my
prefetch folder has never ever exceeded 129 entries. If you clean out the
folder (leave layout.ini) then when you open a program it gets added to the
folder as does every subsequent program - you have gained nothing.
Just let it do its thing.
--
Just my 2¢ worth,
Jeff
__________in response to__________
| Hi,
|
| From what I have read and heard about prefetch, if you
| clean out the prefetch files, it will speed up the boot,
| since it will not preload the files you access often. On
| the other hand, the frequently access files will not open
| up quickly. From what I have heard, it all depends on how
| big your prefetch gets that determines the speed of
| startup. I could be wrong too, but that is what I get
| from reading up on prefetch and responses I have read in
| the News Groups about it.
|
| Jeff
