Can a 32-bit process use more than 3GB of RAM on a 64-bit platform?

Hi

I think the question speaks for itself.  Are there things developers can do to have their 32-bit applications utilize more RAM if it is availble on a 64-bit system (Windows) wihtout having to recompile etc. and if so, how?  Pointers to technical papers will be much appreciated.

Thanks
Vyyk
Vyyk_DragoAsked:
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Kent OlsenDBACommented:
Hi Vyyk,

A 32-bit application is limited to 3GB (2^32) addresses.  That's hard-wired into the definition.  A 32-bit Operating System can use more than 3G, but has to play tricks with memory management by using instructions not available to application (user) code.

If the application does a lot of I/O on temporary files you can create a ramdisk so that the I/O is to memory.  That will help.  It's not really addressing more than 3GB but it is a way to utilize more than 3GB.

The long-term solution is probably to have 32-bit and 64-bit versions with the 32-bit being constrained to the hardware limit of 3GB and the 64-bit free to use the larger memory available to it.


Good Luck,
Kent
Vyyk_DragoAuthor Commented:
Hi Kdo

Thanks for that.  I came across this article some time ago http://pcgamingtips.blogspot.com/2010/04/yes-virginia-32-bit-windows-can-use.html

and was just wondering if that also meant that applications written properly to have large address awareness even as 32-bit processes could be coaxed into using the additional memory a 64-bit system might have available.

Thanks again
Vyyk
Kent OlsenDBACommented:
Hi Vyyk,

Yeah.  Windows, other operating systems, and some system code can utilize memory above the 3GB limit, but your application will likely have been compiled with libraries that don't (or can't) support using more than 3GB.


Kent

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