FAQ/3GB Switch
From VFXPedia
With Fusion 5 and DFX+ 5 came a whole new way to work with our software that allowed our users to really take advantage of the RAM they had on their systems to actively cache the project they were working on. However at the same time version 5's new caching capabilities started to really push the limits of Windows memory management. On systems running 2 GB of RAM or more certain instabilities were found when Fusion or DFX+ started filling up the 2GB of RAM with its cache. In Windows by default any application can only use 2 GB of RAM at most. However under certain versions of Windows, applications could actually use up to 3 GB or RAM if it was available. (A list of the supported operating systems is included below. Please note that Windows 2000 Pro is NOT supported.) To 'activate' this capability you need to add the 3GB switch (instructions below) to your system. Not only does this allow an application to use up to 3GB of RAM if available, but it also makes using 2GB of RAM considerably more stable and reliable as a result.
Please be aware that the 3GB switch will only improve stability on systems with 2 or more GB of RAM, and running one of the operating systems referenced below. Once the 3GB switch has been activated we recommend setting the DFX+/Fusion cache limit to about 80% in the preferences to ensure stable performance.
Adding the 3GB switch is very simple. You first need to locate your machines Boot.ini file which should be located in the root of your main system drive. (Be aware that this file may be hidden and marked as read-only initially.) You will want to open this file in a program such as Notepad to edit it properly.
Alternatively, you can edit the boot.ini settings through the System Properties:
- Right-click on My Computer
- Choose Properties
- Click the Advanced tab
- Click Startup and Recovery Settings
- Click System Startup Edit
You will now see and be able to edit the contents of the boot.ini file. Click OK when done to save your edits.
Note: Before adding the 3GB switch, it is important to note that the switch is very picky, and requires that every device and driver on your system be fully WinXP compatible in order to work at all. If anything in the system is not compatible, Windows will not load at all when restarting with the 3GB switch activated. The only way to then remove the switch from the Boot.ini file so that Windows can load is to either mount the drive in another system and manually change the boot.ini file, or reformat the drive and re-install Windows. Both solutions are far from ideal.
To safely add the 3GB switch we strongly recommend adding a second instance of the OS in the boot.ini, and add the /3GB switch to that second version.
----- default boot.ini without 3GB Switch -----
This is what a default boot.ini file will look like. (This may differ from system to system.)
[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 Pro"
----- updated boot.ini with 3GB Switch -----
This is what the updated version should look like. Notice the /3GB that has been added to the second instance of the OS line.
[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 Pro" multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Pro with /3GB" /3GB
Once you have updated your boot.ini file accordingly and have saved the changes, simply restart your system for the changes to take affect. When your system reboots you will be given the option to choose either the standard Windows XP version or the 3GB switch enabled Windows XP version. If you choose the 3GB version and it fails to allow Windows to properly load, just restart your system and you will be given the two options once again, where you can then choose the standard Windows XP version to load. Either way, if it works or doesn't, you can then remove whatever line you don't need in the boot.ini file. Alternately, you may wish to leave both settings so that you can choose to boot without the 3GB switch should you ever have problems with drivers installed in the future. The boot loader will default to the first option listed in the file. So you may want to put the /3GB option first. You may also wish to lower the timeout value to something quicker so that you don't have to wait for 30 seconds or press Enter with each boot.
Note: The 3GB switch is only compatible with the following versions of Microsoft Windows.
- Windows XP Professional (and greater)
- Windows Server 2003
- Windows Server 2003, Enterprise Edition
- Windows Server 2003, Datacenter Edition
- Windows 2000 Advanced Server
- Windows 2000 Datacenter Server
- Windows NT Server 4.0, Enterprise Edition
For a more detailed explanation of the 3GB switch and usage please visit the following page on the Microsoft website.
http://www.microsoft.com/whdc/hwdev/platform/server/PAE/PAEmem.mspx
In addition:
There is currently a known issue with the 3GB switch and Windows XP SP1, that may cause Windows not to start. A supported fix is available from Microsoft, but it is only intended to correct the problem resulting from this specific setup. For more information including download links to this particular fix please visit the following page on the Microsoft website.
http://support.microsoft.com/default.aspx?scid=kb;en-us;328269
To enable using 3GB RAM by user applications in 32-bit Windows Vista and above:
- Find your command line interpreter cmd.exe (usually located in C:\windows\System32\);
- Right-Click/Run as administrator;
- Enter "bcdedit /set increaseuserva 3072" without quotes, press Enter;
- Restart Windows.
See also:
