CPU L2 Cache Memory setting in Vista

How to Set Vista for the CPU L2 Cache Memory Size​

   Information

The SecondLevelDataCache records the size of the processor cache, also known as the secondary or L2 cache. If the value of this entry is 0, Vista will attempt to retrieve the L2 cache size from the Hardware Abstraction Layer (HAL) for the platform. If Vista fails for some reason to retrieve the L2 cache size from HAL, then it uses a default CPU L2 cache size of only 256 KB. If the default value of the SecondLevelDataCache value is not 0, Vista will use the value (amount of memory) you set instead of 0 (for 256 KB) as the L2 cache size of. This value is designed as a secondary source of cache size information for Vista when the HAL cannot detect the L2 cache from the CPU.

   Note

This sets the SecondLevelDataCache inside the registry.

From Microsoft KB183063:

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. SecondLevelDataCache can increase performance by approximately 2 percent in certain cases for older computers with ample CPU L2 memory (more than 64 MB) by scattering physical pages better in the address space so there are not so many L2 cache collisions. Setting SecondLevelDataCache to 256 KB rather than 2 MB (when the CPU has a 2 MB L2 cache) would probably have about a 0.4 percent performance penalty.

   Warning

Only set the value to what your processor actually has for the L2 cache size. Do not use a larger size than it actually has.

STEP ONE

Find Out the L2 Cache Size Reported by HAL

NOTE: This will show you how to see what the L2 cache size is for your CPU as it is reported to Vista by HAL. This value will be used in STEP TWO below to set the SecondLevelDataCache value for this as a backup in case HAL rarely could not detect the L2 cache from the CPU.

1. Generate a System Health Report.​

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2. Click on the Hardware Configuration arrow on the far right to expand it. (See screenshot below step 3)​

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3. Click on the Devices arrow on the far right to expand it. (See screenshot below)​

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4. Under Devices, scroll down to Motherboard Classes. (See screenshot below step 5)​

A) Click on the + sign to expand​

root\cimv2:SELECT * FROM Win32_Processor.​

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B) Click on the + sign to expand​

Win32_Processor.DeviceID="CPU0".​

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5. In that list, you will see L2CacheSize and the value beside it for it's size to use it in step 6 in STEP TWO below.​

NOTE: For this example you will see 6144 to be used for my CPU's 2x6144 (12MB) L2 size. Now, here's a kicker. The newer Yorkfield Core 2 Quads CPUs use the entire cache for both cores unlike the older CPUs that do not share. So a 2x6144 (12mb) L2 cache would use 12288 (2x6144) instead despite what is reported in Vista for HAL.​

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STEP TWO

Set the L2 Cache Size

NOTE: This will set the SecondLevelDataCache value in the registry, from the value gotten in STEP ONE, as a backup in case HAL rarely could not detect the L2 cache from the CPU and prevent having only a default L2 cache size of 256 KB used as L2 cache size instead by Vista.

1. Open the Start Menu.​

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2. In the white line (Start Search) area, type regedit and press Enter.​

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3. Click on Continue in the UAC prompt.​

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4. In regedit, go to: (See screenshot below)​

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HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

5. In the right pane, right click SecondLevelDataCache and click on Modify.​

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6. Dot Decimal, and type in the value in bold (see table below) for your CPU L2 size from STEP ONE above. (See screenshot below table)​

NOTE: I have a CPU with a 2x6144 (12MB) L2 cache size, so I would use 6144 (Dec) or 1800 (Hex) since it is 2x. See STEP ONE above for how to get the L2 size for your CPU. Now, here's a kicker. The newer Yorkfield Core 2 Quads CPUs use the entire cache for both cores unlike the older CPUs that do not share. So a 2x6144 (12mb) L2 cache would use 122488 (Decimal) or 3000 (hex) instead despite what is reported in Vista for HAL.​

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[TABLE=class:-grid,-width:-400][TR][TD]
Decimal Value
[/TD]
[TD]
Hexadecimal Value
[/TD][/TR]
[TR][TD]
256 KB
[/TD]
[TD]
100 (hex)
[/TD][/TR]
[TR][TD]
512 KB
[/TD]
[TD]
200 (hex)
[/TD][/TR]
[TR][TD]
1024 KB (1MB)
[/TD]
[TD]
400 (hex)
[/TD][/TR]
[TR][TD]
2048 KB (2MB)
[/TD]
[TD]
800 (hex)
[/TD][/TR]
[TR][TD]
3072 KB (3MB)
[/TD]
[TD]
c00 (hex)
[/TD][/TR]
[TR][TD]
4096 KB (4MB)
[/TD]
[TD]
1000 (hex)
[/TD][/TR]
[TR][TD]
6144 KB (6MB)
[/TD]
[TD]
1800 (hex)
[/TD][/TR]
[TR][TD]
8192 KB (8MB)
[/TD]
[TD]
2000 (hex)
[/TD][/TR]
[TR][TD]
12288 KB (12MB)
[/TD]
[TD]
3000 (hex)
[/TD][/TR]
[TR][TD]
16384 KB (16MB)
[/TD]
[TD]
4000 (hex)
[/TD][/TR][/TABLE]

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7. Click on OK to apply.​

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8. Your registry will look like this below for a 2x6144 (12MB) L2 cache memory size.​

NOTE: See STEP ONE above to find out your CPU L2 cache size.​

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9. Close regedit.​

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10. Restart the computer to apply the change.​

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That's it,
Shawn

Related Tutorials

---

• How to Make a Program or Process Run with a Higher or Lower CPU Priority in Vista
• How to Set the Processor Affinity for a Application in Vista
• How to Change the Number of Processors Used at Boot Up in Vista

 

[Case]

Hi again Shawn :D, it is the rookie computer whiz here. I have an AMD Athlon 64x2 4800+. here is what my L2 Cache says from CPU-Z:

Level 2 - 2x512 KBytes

What would I set mine to? Or do I even need to?

Thanks, Casey

 

[Brink]

Hi Casey,

It will be for 1024 KB (1MB)----400 (hex).

Shawn

 

[Case]

ok cool! Are you familiar with PC Wizard 2008? I saw it on the same web site as the CPU-Z. Is it a good thing to have?

Thanks a bunch, Casey

 

[Brink]

Casey,

It's a nice little program for system information. For this program to work properly in Vista, you must check Run this program as an administrator in the Compatibility window for this program's shortcut after it is installed though. For how, see: How to Use Compatibilty Mode in Vista

Shawn

 

[Case]

Ok, but I am a little confused. Do I just right click on the short cut icon and run as admin. everytime I want to use it, or do I actually need to do the steps to put it in compatibility mode. the compatibility mode thing has tumped me. Also, does HDmonitor do the same thing as PC wizard and would I need to run it the same way as PC wizard?

Thanks, Casey

 

[Brink]

Casey,

Using this Compatibility mode option will act the same as right clicking the shortcut and clicking Run as adminstrator, but Compatibility mode will do it automatically for you so you do not have to do it manually each time.

If HDmonitor will not run properly when you click on the shortcut, then you can see if using Compatibility mode will help it.

 

[Case]

Oh I see, that makes complete since. Again thank you so much for your time in responding to my many questions. I am 40 yrs old and have learned more about my computer than I have ever known since finding this site.

Casey

 

[Brink]

Your welcome Casey. I'm glad that this site has been able to help you so much. Just keep posting any questions that you may have. There is always an answer somewhere from someone.

Shawn

 

[Case]

Hey Shawn, I looked for it on the forum, but could not find it. Should I download SP1, and if so where? Also, my other computer has windows XP. Is there a site like this for XP that you trust?

Casey

 

[.Joe]

Hey Shawn, fantastic catch!

I have the q6600 and the reg had zeros. Put in 2000 hex and rebooted.

Thanks for the find. Pure gold

 

[Brink]

Your welcome Joe.

 

[Hachi]

will it result in increasing of temperature?

 

[Brink]

Hi Hachi,

No, it will have not affect on temperature.

Shawn

 

[robydj2007]

it's very usefull man...

thanks

 

[Brink]

Your welcome robydj2007.

 

[storsett]

does this make my computer faster and better?
exstra use of battery?

got an Intel Celeron M 540 and CPU-Z says it has L2 Cache 1024kB..
the regestry has set it at 0 right now...


sorry for the stupid question, got zero cumputer skill's... need to ask sometimes

 

[Brink]

Hi storsett,

It has the potential to prevent a performance loss from your CPU.

If Vista fails for some reason to retrieve the L2 cache size from HAL, then it uses a default CPU L2 cache size of only 256 KB. If the default value of the SecondLevelDataCache value is not 0, Vista will use this value you set instead as the L2 cache size. This value is designed as a secondary source of cache size information when the HAL cannot detect the L2 cache from the CPU.

Shawn

 

[Harkin]

Hiya brink, sorry to bug but I'm slightly confused. I have a C2D E6850(Dual Core) Cpu which has 4096 L2 Cache...Confused as what to put as it's dual core and not sure if it's the same?

 

[Grimace]

Hiya brink, sorry to bug but I'm slightly confused. I have a C2D E6850(Dual Core) Cpu which has 4096 L2 Cache...Confused as what to put as it's dual core and not sure if it's the same?

mate i have the same CPU, and here was my findings (very first reply)

Shawn I just thought id inform that for reson unknown to me the 4mb cache setting isnt 1600.

Its actually 1000. I am unsure as to why cause all the rest are correct.

Cheers
Anthony

So assuming its still the case you will put '1000'

 

[Harkin]

DOH! I thought so but had to confirm, thanks man