Hey where did /3GB go in Longhorn and Vista?

Hey where did /3GB go in Longhorn and Vista?

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If you did not already know there is no boot.ini in Vista/LH.  So how do you set usermode space to 3GBs?

If you recall on x86 platforms there is 4GBs of addressable VM space.  So by default that is split up equally.  2GBs for kernel mode and 2GBs for use mode.  Now this is usually fine, but if you have a server that could use more usermode space like domain controllers, SQL servers, exchange sevrers, etc.  You could really use another GB for caching of the database in user mode.  Or you could suck it up and by an x64 machine.

In 2k3 you would do this by using the /3GB switch in the boot.ini which would split the VM, giving 1GB to kernel and 3GBs to user.  Allowing LSASS to cache more of the database on a domain controller for example.

So how do we do this in Vista and LH?  It's actually pretty simple: 

BCDEDIT /Set IncreaseUserVa 3072

You do not have to specify the boot selection GUID.  If you do not specify, it will modify the current selection, which is what you want to do anyways.

 

 

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Comments
  • Eduardo, the /3GB switchdoes not increase the physical memory that the OS can see it just splits the virtual memory up so that user mode prcoesses see 3GB of the VM space.  If you are having issues seeing all the RAM in your system, I'd check some of the forums on the internet for your desktop model.

    -Brad

  • Thank you Brad for your patience and solid information

  • My 4G only read as 3 on a 32 bit Vista...common situ, I see...when I run BCDEDIT I get: The boot configuration data store could not be opened. Access is denied.

    You mentioned in a prior post running that from "elevated" command prompt...admit I'm clueless in this arena...help?

    Thanks...

  • Hey Sharon, just find the command prompt link in the start menu and alt-click and choose "run as administrator"

  • Hacking Visual Studio to Use More Than 2Gigabytes of Memory

  • Can I connect my USB wireless aircard (Sierra 875U) to a desktop PC and the PC to a wireless router and use the connection for both my desktop & laptop? Or vice versa--aircard to router and ethernet to PC, laptop?

  • should this work with 8GO RAM ??

    i mean could i take full advantage of 8go ram installed ???

  • Hi Raiden, to take advantage of that much RAM you should use an x64 OS.  The 3GB switch is for x86 systems, and wouldn't help with a situation where you want to use 8GBs.

  • I am unable to use bcdedit I get permishion denied I am the Admin? Tried C: c:windows

    c:windows/boot

    Vista 32

    Larry

  • Perfect, thx for this. Helps us out a great deal here when a particular mem-hungry commercial game engine kept running out of memory for non-programmers ( programmers seemed to have this set already somehow - maybe Visual Studio does it sneakily during install?). Whatever, worked fine, and gained our people nearly another 1GB to work with.

  • I have a CORE i7 with 8GB RAM and I am running Windows 7. How can I change the settings for my Visual Studio 2008? I tried this appriach and the command was not accepted.

    Thanks!!

  • I have a CORE i7 with 8GB RAM and I am running Windows 7. How can I change the settings for my Visual Studio 2008? I tried this appriach and the command was not accepted.

    Thanks!!

  • Great help. thanks :)

  • Would it be a good idea to use this in vista that has only 3GB of ram ?

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