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Solved: Enabling 3GB switch?

Discussion in 'Windows XP' started by Kizko, Dec 14, 2010.

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  1. Kizko

    Kizko Thread Starter

    Joined:
    Sep 4, 2010
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    Hey, how do you enable the 3GB switch on your XP? I've read some instructions on how to, but they were very clear.
    Anyone got any idea?
    Thanks in advance.
    I'm running with 4GB of RAM and Home Edition, if it helps.
     
  2. AnthonyLordi

    AnthonyLordi

    Joined:
    Apr 26, 2010
    Messages:
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    • Right-click My Computer. Click Properties.
      [*]In the System Properties dialog box, click the Advanced tab.
      [*]On the Advanced tab, under Startup and Recovery, click Settings.
      [*]In the Startup and Recovery dialog box, under System startup, click Edit. The Windows boot.ini file will be opened in Microsoft® Notepad.
      [*]Create a backup copy of the boot.ini file. Note: Boot.ini files may vary from computer to computer.
      [*]Select the following line in the boot.ini file:
      [*]multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /fastdetect

      [*]Press Ctrl+C to copy the line and then press Ctrl+V to paste it immediately below the original line.
      [*]Note: Your text string may be different from the text string in this solution, so be sure to copy the text string from your boot.ini file, and not the text string included here.
      [*]Modify the copied line to include “ /3GB”, as shown in the following example:
      [*]multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional 3GB" /3GB /fastdetect

      [*]Note: Do not overwrite any existing lines.

      [*]Save and close the boot.ini file.
      [*]Click OK to close each dialog box.
      [*]Restart your computer.
      [*]During startup, select the 3GB option. If you do not select the 3GB option, the system will default to the 2GB total memory setting.
      [*]Note: If problems occur during startup, you may need to update some of your drivers.
     
  3. flavallee

    flavallee Trusted Advisor

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    May 12, 2002
    Messages:
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    First Name:
    Frank
    Right-click MY COMPUTER, then click Properties. What's listed for the amount of RAM?

    You're probably not going to see any speed or performance increase with more than 2 GB of RAM with Windows XP(32-bit), so editing the BOOT.INI file to show 4 GB isn't worth the risk.

    ----------------------------------------------------------------
     
  4. TheOutcaste

    TheOutcaste

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    9,028
    Are you actually running software that can take advantage of using the /3GB switch? If your software isn't written for it, it won't make a difference.
    It can actually hurt performance, as you will be reducing the RAM that is available for the OS to use. You can actually end up forcing the kernel to use the swap file even though there is unused RAM available.
     
  5. Kizko

    Kizko Thread Starter

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    Sep 4, 2010
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    As in software do you mean Windows XP Home Edition? I'm not sure if it does or not. Also, dxdiag says I'm running 3.3GB of RAM. The only reason I need this 3GB switch is that GTA IV brings up an error about a memory error, and Rockstar's support website says that enabling the switch should fix it.
     
  6. TheOutcaste

    TheOutcaste

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    Not the OS, the application you are running, sounds like GTA IV in this case. All you can do is try it and see if it resolves the issue.
    Adding a 2nd line to the boot.ini file as AnthonyLordi suggests would let you tweak the settings as needed, while still being able to boot without the /3gb switch if the system should fail to boot with it present.

    You can't change the 3.3 GB number. The other 0.7 GB of the 4 GB total address space is being used by the hardware/video RAM, it's not available for Programs or the OS.

    Using the /3GB switch will let the program use 3 GB of RAM instead of just 2 GB by limiting the kernel to using just 1 GB. But if .7 GB is being used by the hardware, the kernel may have only 0.3 GB it can use, which may have adverse effects.

    You may need to also use the /userva switch to reduce the User Memory from 3 GB to a little less so the kernel will have a bit more available. See this KB article for info (it's a bit technical but shows the syntax for the switch):
    How to use the /userva switch with the /3GB switch to tune the User-mode space to a value between 2 GB and 3 GB

    For example, using /3GB /userva=2900 assigns 2.83 GB to the User space (programs) giving back .17 GB to the kernel.
     
  7. Kizko

    Kizko Thread Starter

    Joined:
    Sep 4, 2010
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    Alright, so my boot loader at the moment is:
    ____________________________________________________________________________________
    [boot loader]
    timeout=30
    default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /fastdetect


    So when I change it to the new Boot.ini it should look like:
    ____________________________________________________________________________________
    timeout=30
    default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /fastdetect
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /3GB /userva=2900 /fastdetect


    Is this right?
     
  8. TheOutcaste

    TheOutcaste

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    Aug 7, 2007
    Messages:
    9,028
    You left out the first line, but other than that it's OK. I'd suggest changing the Description so you can tell them apart though. You can also add more than one line, if you want to try one without the /userva switch. It might not be needed:
    Code:
    [boot loader]
    timeout=30
    default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /fastdetect
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="[COLOR=Red]3GB no userva[/COLOR] XP Home Edition" /noexecute=optin /3GB /fastdetect
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="[COLOR=Red]3GB with userva[/COLOR] XP Home Edition" /noexecute=optin /3GB /userva=2900 /fastdetect
     
  9. Kizko

    Kizko Thread Starter

    Joined:
    Sep 4, 2010
    Messages:
    24
    Worked perfectly, but it didn't fix the problem. Must be something else, so I might post in the gaming section. Thanks for all the help though!
     
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