Enabling the 3 GB Feature

Memory Usage
You can perform certain actions to decrease the possibility of instability in Revit Systems due to operating system memory usage.

To ensure stability, you can:

• Restart Revit Systems regularly.
• If you receive a message that your current session's memory usage is approaching the operating system limit, it is recommended that you save your work as soon as possible and restart Revit Systems. If you are using a workshared environment, it is recommended that you save your local file, restart Revit Systems, and then save to central.
  
• Enable the 3 GB feature on your Windows® operating system to improve performance.
• Run on a Windows 64-bit operating system.
• Reduce the number of loaded DWG and RVT links.
• Reduce the number of loaded RVT and RFA files.
• Limit the number of views open. If you have multiple views open, you can quickly close all hidden views by clicking Window menu ➤ Close Hidden Windows.
  

Enabling the 3 GB Feature

Typically, Microsoft Windows® reserves 2 GB of the 4 GB virtual address space of any process for the operating system and leaves the remaining 2 GB for the application process (including the space for the code pages, the stack, and all dynamically allocated memory). The 3 GB feature divides the memory space differently, providing 3 GB for the application and 1 GB for the operating system. Before enabling the 3 GB feature, see “3 GB Feature Considerations” at the bottom of this page.

To enable the 3 GB feature:

1. Open the boot.ini file. This file is typically located in C:\boot.ini.
2. Copy the original line, then modify the copied line to add the option (/3GB) and the display string that identifies the boot option.
3. The line to copy and the modified version of the line are shown below. The modified portions of the copied line are in bold.

• multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /fastdetect
• multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional 3GB" /3GB /fastdetect
  

When you start your computer with the modified boot.ini file, you see the following options to select from:

• Microsoft Windows XP Professional
• Microsoft Windows XP Professional 3GB
  

After you enable the 3 GB feature, you should verify that you have sufficient virtual memory allocated for your purposes.

Verifying Virtual Memory Allocation

1. In Windows XP, click Start ➤ Settings ➤ Control Panel.
2. In the Control Panel, double-click System.
3. In the System Properties dialog, click the Advanced tab.
4. In the Performance field, click Settings.
5. In the Performance Options dialog, click the Advanced tab.
6. In the Virtual Memory field, click Change.
   

Your system should have at least 3 GB set aside for the paging file size to fully utilize the available address space. Every concurrently running application is sharing the available paging file size, so setting to something more than 3 GB (such as 4 GB) is recommended.

3 GB Feature Considerations

■ This feature is only supported on Windows XP SP2.
■ When the 3 GB feature is enabled, your operating system has less memory space. It is not completely clear what implications this may have on Windows XP, so be cautious with regard to the total application load placed on Windows while running in this mode. If you do not require the larger address space, it is recommended that you do not enable this option.
■ At least one graphics card driver version is known not to work with 3 GB. This is ATI Fire GL 8800, driver version 6.12.10.3035. If you experience a crash, restart your computer without the /3GB option and see if upgrading to the latest graphics card driver resolves the issue.