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Below is what I understand, please correct me if i'm wrong about the 3GB part?

  • a win32 application's virtual memory address space is limited by 4GB.

  • Of the 4GB memory address space each process gets, only 2GB is actually available for the program to use; the other 2GB is reserved for use by the kernel.

  • The /3GB boot option can allow some programs to use more memory address space.

If such an win32 application is running on a Win64 OS,

  • does the above 4GB limitation of total virtual memory address space accessible still applies?

  • does the 2GB limitation still applies?

  • is the /3GB option still available?


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up vote 5 down vote accepted

Referring to the table here, we can see that a 32 bit application can have three different virtual memory limitations:

A 32 bit application linked with the /LARGEADDRESSAWARE flag on x64 Windows will get 4GB to itself.

A 32 bit application linked with the /LARGEADDRESSAWARE flag on x86 Windows with the /3GB boot flag will have 3GB to itself.

In all other cases, the 32 bit application will get the default 2GB/2GB app/kernel split..

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Yes, depends, no.

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There is no /3GB option on a 64-bit OS, but none is needed. LAA 32-bit applications can always use a full 4GB of virtual memory on 64-bit versions of Windows. – David Schwartz Feb 21 '12 at 7:03
Er, not quite "always". A 32-bit app will have to be linked with /LARGEADDRESSAWARE to use 4GB of virtual memory. Otherwise it is limited to 2GB. – Jamie Hanrahan Aug 8 '14 at 20:32

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