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CPU L2 Cache Memory setting in Vista

  1. #1
    CPU L2 Cache Memory setting in Vista

    CPU L2 Cache Memory setting in Vista
    How to Set Vista for the CPU L2 Cache Memory Size
    CPU L2 Cache Memory setting in Vista

    How to Set Vista for the CPU L2 Cache Memory Size

    information   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   Note
    This sets the SecondLevelDataCache inside the registry.

    From Microsoft KB183063:

    Quote Originally Posted by 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   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.

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

    3. Click on the Devices arrow on the far right to expand it. (See screenshot below)
    -arrows-jpg
    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.
    B) Click on the + sign to expand
    Win32_Processor.DeviceID="CPU0".
    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.
    -system_health_report-jpg




    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.

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

    3. Click on Continue in the UAC prompt.

    4. In regedit, go to: (See screenshot below)
    Code:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
    5. In the right pane, right click SecondLevelDataCache and click on Modify.
    -before_reg-jpg
    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.

    Decimal Value Hexadecimal Value
    256 KB 100 (hex)
    512 KB 200 (hex)
    1024 KB (1MB) 400 (hex)
    2048 KB (2MB) 800 (hex)
    3072 KB (3MB) c00 (hex)
    4096 KB (4MB) 1000 (hex)
    6144 KB (6MB) 1800 (hex)
    8192 KB (8MB) 2000 (hex)
    12288 KB (12MB) 3000 (hex)
    16384 KB (16MB) 4000 (hex)

    -modify-jpg
    7. Click on OK to apply.

    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.
    -after_reg-jpg
    9. Close regedit.

    10. Restart the computer to apply the change.
    That's it,
    Shawn





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    Brink's Avatar
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    Applies to

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  2. #1


    Join Date : Apr 2007
    Gold Coast, AUSTRALIA
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    Re: CPU L2 Cache Memory setting in Vista

    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

      My System SpecsSystem Spec

  3. #2
    Brink's Avatar

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      Thread Starter

    Re: CPU L2 Cache Memory setting in Vista

    Anthony,

    Thank you.
    Nice catch. It has been updated.

    Shawn

      My System SpecsSystem Spec

  4. #3


    Join Date : Nov 2007
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    Vista Home Basic
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    Re: CPU L2 Cache Memory setting in Vista

    How do you determine L2 cache size to make these mods

      My System SpecsSystem Spec

  5. #4
    Brink's Avatar

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      Thread Starter

    Re: CPU L2 Cache Memory setting in Vista

    Hi Maineearle,

    You need to look up your CPU's specs to see that it says. Go to the manufacturer's website to do so.(EX: Intel or AMD) You can find the model number to look it up with by right clicking Computer (in Start menu) and click Properties. You can also find the model number in System Information.

    Shawn

      My System SpecsSystem Spec

  6. #5
    z3r010's Avatar
    Join Date : Oct 2005
    Standish, Lancashire, England
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    Re: CPU L2 Cache Memory setting in Vista

    Wouldn't something like cpuid give you the info

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  7. #6
    Brink's Avatar

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      Thread Starter

    Re: CPU L2 Cache Memory setting in Vista

    Thank you,

    Why, yes it will. It's a standalone EXE program. No need to install, just run the EXE. You can find the information under the CPU tab under Cache Level 2.

    http://www.cpuid.com/cpuz.php

    Shawn

      My System SpecsSystem Spec

  8. #7
    Violent Ken's Avatar
    Join Date : Nov 2007
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    Re: CPU L2 Cache Memory setting in Vista

    q6600 has 2x 4096 L2, so i put in 1000?
    it's set to 0 currently

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  9. #8
    Asky's Avatar
    Join Date : Jun 2007
    Atlanta,USA
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    india

     

    Re: CPU L2 Cache Memory setting in Vista

    ^i dunno if we can put 2000(since brink hasnt mentioned it) so better put 1000 to be safe.

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  10. #9
    Brink's Avatar

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      Thread Starter

    Re: CPU L2 Cache Memory setting in Vista

    Quote Originally Posted by Violent Ken View Post
    q6600 has 2x 4096 L2, so i put in 1000?
    it's set to 0 currently
    Hi Violent Ken,

    This means that you have 8 Mb shared cache between the 4 cores. You should use 2000 as the value. I updated the tutorial for this.

    You can read more on your Intel Core 2 Quad Q6600 processor here:

    http://www.intel.com/products/processor/core2quad/index.htm


    Quad-Core Processor:
    Provides four complete execution cores in a single processor with 8 MB of L2 cache and a 1066 MHz Front Side Bus. Four dedicated, physical threads help operating systems and applications deliver additional performance, so end users can experience better multi-tasking and multi-threaded performance across many types of applications and work loads.
    Intel Advanced Smart Cache:
    Shared Level 2 cache across each pair of cores that can be dynamically allocated to each processor core, within the pair can access data from fast L2 cache, significantly reducing latency to frequently used data and improving performance.
    Shawn

      My System SpecsSystem Spec

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CPU L2 Cache Memory setting in Vista
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