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

 

[Brink]

Good evening everyone. My processor is a Intel Pentium Dual core T3200 @ 2.0GHZ and I was skeptical the settings required to utilize the tip.

Hello Taheed, and welcome to Vista Forums.

You can use the value that you find listed using STEP ONE in the tutorial as the decimal number in step 6 of STEP TWO.

Hope this helps,
Shawn

 

[Taheed]

Thanks bud, so I recently discovered that my L2cachesize was 1024. So in decimal I will use 1024 and in Hex I would put 400?

 

[Brink]

You're welcome Taheed. Yes, that would be correct.

 

[pacinitaly]

I can no longer create a report I get the attached error
service is on
also, no key in the registry

.... every day another issue

 

[Brink]

Hello Pacinitaly,

Are you logged in as an administrator?

If you are, then as a test, create a new administrator account to see if it runs properly in it. If it does, then you can copy the contents of your old account's C:\Users\(User-Name) folders into the corresponding new account's C:\Users\(User-Name) folders.

Hope this helps,
Shawn

 

[pacinitaly]

thanks Shawn,
I'll try in a little while, I'm doing a clone at the moment on the vista laptop

 

[pacinitaly]

I tried, no go
I also tried to access via the hidden admin acct
net user administrator /active:yes
not work... oh well can't wait for 10/22/09


thanks Shawn again


Carmine


OK I read Error When Generating System Health Report - Windows Vista Performance & Maintenance
from a post from you

and did as stated. I was able to view my l2 cache ( which is 4096 )

I had to create a dword in the registry.


we'll see what happens

I have read all over the web and YOU only found the solution... maybe it should be a tutorial


Thanks again

Carmine


PS I still can't generate a system health report the correct way as stated above but...

 

[Brink]

Carmine, I'm happy to hear that you got it sorted.

 

[johnmunch]

Hi all,
After going throw what you said it seems easy at first but then I see I have a ---> Amd 64 Phenom 8550 Triple-core processor 2200 family 16 Model 2 Stepping 3 <--- and after running the test it is set at 512, now at first I thought to set it to 600 Hex but then remmbered seeing the warning about setting it wrong, So here I am for your great knowledge. I would also like to know about L3cacheSize and L3cachespeed as that also shows up but is set to 0 on both, but did read in a post about it not being suppoted ( I beleave ) is that right? .

Cheers.

 

[Brink]

Hello John,

Looking at AMD's website, I only see the 8650 and 8450 CPU listed. However, they both hava 512MB L2 cache. Your's would to, so this is correct for how it is reporting to you and I would not change it. It is this low since your CPU as a 2048MB L3 cache. Currently there is no method to manually changing the L3 cache settings.

It looks like you do not need to change anything.

Hope this helps,
Shawn

 

[johnmunch]

Thanks for your help Brink. Save's me burning out my cpu.

 

[Brink]

You're welcome John.

 

[TuNaY]

I have Core2Duo T9600 at 2.80Ghz 6MB cache. So I should set it at 1800 ?

 

[Brink]

Hello TuNaY,

Since your T9600 CPU has a 6MB L2 cache, then yes you would want to use 1800 with the HEX option.

 

[TuNaY]

Hello TuNaY,

Since your T9600 CPU has a 6MB L2 cache, then yes you would want to use 1800 with the HEX option.

Hi
Thanks again
I wanted to make sure

 

[Brink]

You're welcome TuNaY. No problem.

 

[Shaythong]

Hello Brink, I have a AMD Turion 64 X2 2.0GHZ laptop CPU. The system health report says that my L2CacheSize is 1024. Do I need this or does Vista already know that my L2 cache is 1024 and I do not need this fix?

Also for the "changing the Number of Processors Used at Boot Up in Vista" fix, do I need this? I heard it was just a fake thing and Vista will detect it automatically.

 

[Brink]

Hello Shaythong, and welcome to Vista Forums.

Most likely you may not need to change your CPU L2 cache as per in the information box at the top of the tutorial. You can check in step 6 of STEP TWO to see if you have the 1024 MB size set though.


By default, Vista will use all of your CPU cores or processors. So you will not need to change this setting. However, some people have swore that checking the box to use all processors had increased their performance though.

Hope this helps,
Shawn

 

[Shaythong]

Thank you for responding.

I tried step two part 6 but the registry value was "0" so I'm not sure if it is 1024 MB.

To the processor startup options: I think that only applies to people with more than two processors (dual-core) right? Did you experience an increase in performance?

Thank you.

 

[Brink]

You could set it to 1024 MB (Decimal) in step 6 of STEP TWO to have it set for the correct size for your CPU.


The number of processors option is for people that have multiple processors or a multicore processor, but you can read more about all that and my results here instead.