Friday, June 5, 2009

Being Civil: Performance tweak for 32-bit XP or Vista with 3GB switch enabled

Being Civil: Performance tweak for 32-bit XP or Vista with 3GB switch enabled:

Back in January, Justin wrote a great post on "The basics of RAM and 32/64-bit environments." I wanted to add another tip for those of you on 32-bit Operating Systems who have enabled the 3GB switch and still have some problems. This will not solve all issues, but may provide some relief. If you just set the 3GB switch, you force the OS to allocate a full 3GB of virtual memory for application use, and the OS (kernel) is limited to 1 GB.
By setting the /userva switch, you give the OS a bit of space back. This can be useful if you are running into display issues with your graphics card, as some video adapter drivers with onboard RAM need more than 1GB of kernel address space. Or we have found sometimes drawings that would not open with just the 3GB switch will open successfully if you tweak it back a touch using /userva and give the OS a bit more breathing room.
The Microsoft Documents are here:
Windows XP 32-bit (don't worry, it says for Windows Server 2003, but is also applicable to Windows XP 32 bit).
Windows Vista 32 bit
Microsoft recommends setting the variable between 2800-2900 for optimal performance.
Our Technical Solution for enabling the 3GB switch on XP and Vista 32 bit OSs is here. (Note for Vista, all it is doing is setting the UserVa setting to 3072; you can set this value lower, as mentioned in the Microsoft document link above).

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