EnablePrefetcher


 * EnablePrefetcher **

[HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\MemoryManagement\PrefetchParameters] "EnablePrefetcher"

//Myth// - "Setting any value higher then 3 to EnablePrefetcher will improve performance."

//Reality// - "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. This is a new feature in Windows XP which improves application load times and Windows boot times automatically. The slower your system and the larger an application, the more Prefetching helps. Even high end systems benefit from prefetching with large, slow loading applications, such as large games. By default Prefetching is enabled in Windows XP and already configured optimally. The following list describes the different possible values for the EnablePrefetcher registry key.

0 = Disabled

1 = Application launch prefetching enabled

2 = Boot prefetching enabled


 * 3 = Applaunch and Boot enabled (Optimal and Default)**

By default the Prefetcher is set to a value of 3 in Windows XP. Values such as 4, 5, 6 ect... do not exist and are thus useless. Leave this at the default value of 3 which is already optimal for maximum performance on both Windows XP Boot and initial application launches." –

This is completely false and is spread by people who do not understand how Windows XP Prefetching works. The slower the system the more it will benefit from Prefetching. 64 MB systems will suffer due to insufficient RAM, reducing but not eliminating Window XP's prefetching benefits. 128 MB is the recommended minimum for optimal prefetching performance.
 * Low Memory Systems** - Recommendations to disable Prefetching on low memory systems (128 MB - 512 MB) is based on the fallacy that portions of application code are preloaded into memory before the application load is initiated during Windows startup.

Recommendations to set the EnablePrefetcher value to 2 to improve boot performance is based on the fallacy that portions of application code are preloaded into memory before the application load is initiated during Windows XP startup. This is completely false and is spread by people who do not understand how Windows XP Prefetching works. Only the files used during boot will be Prefetched. The Prefetch folder is not a cache. Windows XP will boot in the exact same amount of time with either value 2 or 3, the only difference with 2 is that now all of your initial application launches will not be Prefetched and thus load slower. The default value of 3 in no way negatively affects Windows XP boot times. Leave the value at 3 for optimal Windows XP boot and initial application launch times.
 * Boot Performance** –