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nickyhoward55

Member
Joined
Jun 25, 2005
i dont know if this has been posted b4, if it has im sorry. but it works for me and i thought id share it with you.

please use a program like cpu-z to get ur L2 cache size

For users of Windows 2000 or XP you actually have to tell the OS what size L2 cache your processor has otherwise it won't be used properly! Luckily it's fairly easy to fix.

Click on the Start button then go to run. From there type REGEDIT and press the "Ok" button. After it opens the Registry Editor follow this path. hkey_local_machine, System, CurrentControlSet, Control, Session Manager, Memory Management

Once you're in the Memory Management folder look for the DWORD value
secondleveldatacache.
Right click on that and go to modify. Very important you have to change the Base from Hexidecimal to Decimal before modifying the values. After that's done just punch in your L2 cache size so if you're using an AthlonXP (Thoroughbred) since the CPU has 256KB L2 Cache you enter 256. For Duron's enter 64 and for P4 Northwood's enter 512.
After that's done you should notice your programs now have quite a bit more zip and the system is less sluggish because Windows now knows how to use your L2 cache properly.
 
In early versions of XP that was a known flaw, but in later versions that is no longer a problem. It is definitely worth checking to make sure you are getting the benefit of your entire L2 cache.
 
[SaS]hornet said:
After that's done you should notice your programs now have quite a bit more zip and the system is less sluggish because Windows now knows how to use your L2 cache properly.

Have you tested that and compared with benchmarks?
 
The only thing I can see that is questionable, is the above linked page says that anything after a PII doesnt use this feature, which would say to me that the rest of this post is useless. :)

It looks to me like 0=auto detect which is the default. If it is set to your Cache size (IE: 512, 1024, 2048) then it will force that size. If it is set to 0 and can't auto detect, it will run at default using 256KB. So, if you have it set to 0, it should auto detect how much cache you have, but if it cant detect it, it will only use 256KB. If you manually set it to your cache amount, it will force it to use that amount.
 
I know you are trying to help, but I would just ignore any registry tweaks you see on the internet that say it will increase performance. It is safe to assume that it will not. Most tweaks do not help at all. This is one tweak that will not increase performance. Systems using a Pentium II or newer CPU are not effected by using this "tweak" as the HAL is perfectly capable of retrieving the L2 cache size. SecondLevelDataCache is designed as a secondary source if the HAL cannot detect the L2 cache.

In early versions of XP that was a known flaw

No, it wasn't.
 
Just because it's posted at that forum doesn't mean it's correct. People are quick to claim performance increases without backing them up. Quite a powerful placebo effect I imagine.
 
"This is not related to the hardware; it is only useful for computers with direct-mapped L2 caches. Pentium II and later processors do not have direct- mapped L2 caches." (from the MSKB article mentioned)

Just in case you are paranoid that your chip is somehow direct-mapped though, it's a fairly simple matter to find out. Get CPU-Z, and go to the "Cache" tab. The "Associativity" of the L2 is what you're looking for:

"If the replacement policy is free to choose any entry in the cache to hold the copy, the cache is called fully associative. At the other extreme, if each entry in main memory can go in just one place in the cache, the cache is direct mapped. Many caches implement a compromise, and are described as set associative." CPU Cache (Wikipedia)

My Prescott isn't direct mapped (just as the MSKB would lead you to believe), but rather 8-way associative.

JigPu
 
i noticed this tweak on another website and didnt bother with it, until there were around 50 replys syaing that it works. if it doesnt harm anything, and doesnt decrease the performance of windows then its a worthy tweak.
 
the microsoft knowlage base artical...
APPLIES TO
• Microsoft Windows NT Server 4.0 Standard Edition
• Microsoft Windows NT Workstation 4.0 Developer Edition
• Microsoft Windows NT Server 4.0 Enterprise Edition

so i dont know if that 0 for 256 or 1 for 512 aplies on win2k and xp

edit: i have that value set to 200 i have 2 cpus with 512 cache on them do i set it to 400 (1024kb)????
 
Last edited:
[SaS]hornet said:
i noticed this tweak on another website and didnt bother with it, until there were around 50 replys syaing that it works. if it doesnt harm anything, and doesnt decrease the performance of windows then its a worthy tweak.
How does not hurting anything make it a worthy tweak?
 
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