Enabling 3GB switch on Windows XP or Windows Vista

Many of Autodesk's applications, including Navisworks, are able to take advantage of the 3GB functionality switch.

Advanced users may know that the virtual address space of processes and applications is still limited to 2 GB unless the /3GB switch is used in the Boot.ini file. When the physical RAM in the system exceeds 16 GB and the /3GB switch is used, the operating system will ignore the additional RAM until the /3GB switch is removed. This is because of the increased size of the kernel required to support more Page Table Entries.

Note: Only applications that use IMAGE_FILE_LARGE_ADDRESS_AWARE in the process header can take advantage of this functionality.

Enable the 3GB switch on Windows XP

• 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.

Enable the 3GB switch on Windows Vista

• Right-click Command Prompt in the Accessories program group of the Start menu. Click Run as Administrator.
• At the command prompt, enter "bcdedit /set IncreaseUserVa 3072"
• Restart the computer.

Disable the 3GB switch on Windows Vista

• Right-click on Command Prompt in the Accessories program group of the Start menu. Click Run as Administrator.
• At the command prompt, enter "bcdedit /deletevalue IncreaseUserVa"
• Restart the computer.

For more information on the 3GB switch, refer to the following Microsoft MSDN article:

http://msdn2.microsoft.com/en-us/library/ms791558.aspx

Please note that only skilled Administrators or personnel should perform the above stated procedure. I cannot be held responsible for any problems occurring on your machine/s as a result of the afore stated.

As always, thorough research of the content and it's impact is highly recommended before proceeding.

Thank you.

 

Comments

[Stefaan Boel]

Joseph,

You have to indeed be carefull with messing with the boot.ini file.
Furthermore, in Windows XP you better set a lower value dan 3GB because these days video cards use a lot of memory when using Direct3D.
But with the new drivers and graphics database, I was able to move to OpenGL. It's up2speed now!

[Volker Joseph]

Thank you for your feedback.

Exactly why I pointed out that only skilled people should perfom this process.

Appreciate you sharing your personal experience.

[DrVal]

/3gb switch doesn't work with Inserting Images using Map3D (LDT, C3D, or just Map).

You have to reboot out of the /3gb to make it work.

[Jerry]

I appreciated this article. It was probably the best explanation I found while configuring two computers to run Adobe CS3. I was wondering why they only saw two gigs of memory when there were three present.

[macunni2]

Thanks man!

More PC users need to know about this and it is impossibly indecent that the memory you pay for is not automatically utilized.

Thanks for your time,

[Larry Miller]

The author is correct in stating that this switch effects the virtual address space. But the most recent comment is wrong, this switch has nothing to do with how RAM is utilized. Even without this switch a system will be able to make full use of 3GB or even more RAM, if it can be provided. This setting only effects the normal division of virtual address space which is totally independent of how RAM is utilized.

The setting has a downside and should only be used when an important application requires or will benefit from the larger virtual address space. It restricts the system cache which will have a negative influence on system performance. There are other issues as well.

Larry Miller
Microsoft MCSA

[Ralph Sanchez]

I've found that this causes more trouble than it solves under 32 bit XP with Nvidia Quadro cards. Even after constantly tweaking the userva value, we've never been able to arrive upon a configuration that works.

[Quick Loans]

Any news about this on Windows 7?

[Andreas E.]

Note: *NEVER* use said switch together with /PAE. It's just plainly silly. Don't.

[Injury Claims London]

The memory is not utilized automaticly, so people need to know when buying.

[David]

I had a little trouble enabling 3GB until I figured out I had introduced a syntax error that made logging in impossible. Be sure to tell folks that there needs to be a space before the switch, just like if you were doing a command line entry thus:
.../fastdetect[space]/3GB

From another source, it's recommended that you change VM settings to 4096MB in the (XP) System Properties dialog Advanced tab
ref: http://www.finitesolutions.com/Support/Enabling3GB/tabid/70/Default.aspx

[James]

I've found that this causes more trouble than it solves under 32 bit XP with Nvidia Quadro cards. Even after http://www.hotfilemediafire.com constantly tweaking the userva value, we've never been able to arrive upon a configuration that works.

[Reg cleaner]

I never tried windows vista, it's big disaster, I prefer Windows 7.

[Ratish]

This is a very nice article.. very well explained.

Correct me if Im wrong, the correct syntax is "Microsoft Windows XP Professional 3GB" /3GB /fastdetect note the /3GB before /fastdetect. I was using it the other way ans could not get the 3GB effect on the win XP system

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I appreciated this article. It was probably the best explanation I found while configuring two computers to run Adobe CS3. I was wondering why they only saw two gigs of memory when there were three present.

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Be sure to tell folks that there needs to be a space before the switch, just like if you were doing a command line entry thus:

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Windows XP is the user friendly operating system but in windows vista there are lots of security options so i didnt like it much this post gives some good information thanks for sharing this post