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st: Another 2-bit 64-bit question


From   "David Elliott" <dcelliott@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Another 2-bit 64-bit question
Date   Mon, 20 Aug 2007 16:16:20 -0300

I have scanned the archives and have found many permutations of 32/64
bit questions, but not one precisely covering this point:

Does 32 bit Stata Windows running on a 64 bit machine have access to
more memory than when running on a 32 bit machine?  I am aware of the
4Gb address-space barrier, and that 32 bit Windows has only 2Gb of
"user" memory space which translates to 1.2-1.5 Gb maximum memory
space for running Stata.

64 Windows can run 32 bit programs using a 64 to 32 bit WOW (Windows
on Windows) process which sets up a 32 bit sandbox for the program to
play in.  What differs from the running on a 32 bit Windows OS is that
the 32 bit process doesn't have to share the user memory space with
the OS and other programs which would theoretically allow it to access
the full 2 Gb of user memory.  In fact, if a 32 bit Windows program is
64 bit aware (despite running in 32 bit mode) it can theoretically
access the full 4 Gb memory space.

(Those wishing to explore the arcana of 32 bit computing on 64 bit
systems may consult:
http://msdn2.microsoft.com/en-us/library/aa384249.aspx
with special reference to the memory section:
http://msdn2.microsoft.com/en-us/library/aa384219.aspx
Finally, there is an excellent discussion by Kerry Kammire and Bill
Gould of StataCorp regarding performance issues of 32 vs. 64 bit
Stata:
http://www.stata.com/support/faqs/win/64bit2.html )

While I realize I could have addressed this question directly to
Statacorp, I know there are a lot of 32 - 64 bit questions within the
community, and sometimes misunderstandings regarding how Stata
functions in various environments.  I work with datasets that often
skirt the memory limits requiring me to shut down all other programs,
run a memory defragmenter, and perform various incantations in order
to get things to work.  Since I am in the market for a new computer,
I'm trying to scope out various options and am considering a jump to a
64 bit processor and OS.

-- 
David Elliott
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