Re: Can 32-bit apps possibly access more than 4GB ???

Rolf Magnus <>
Sat, 19 Dec 2009 10:25:08 +0100
Michael Mol wrote:

On Dec 19, 12:15 am, Jonathan Lee <> wrote:

On Dec 18, 11:38 pm, "Peter Olcott" <> wrote:

I am looking to create an application that needs lots of
memory. I don't want to write it as 64-bit code because
32-bit machines or 32-bit Windows probably could not run
these apps. In the ideal case I would like to write my
application such that it would run on any machine, and could
take advantage of whatever memory was available. What is the
best way to do this?

Not really a C++ question, but whatever...

- You'll probably have to do something like that anyways since
no reasonable OS will give you that much memory. I think
Windows will cough up 2GB at most.

Windows will offer as much as 3GB for userspace in a process if it's
marked as Large Address Aware in its manifest.

However, many 32 bit versions of Windows won't access more than about 3 GB
of physical memory in total.

- I've never heard of a 32-bit machine w/ more than 4GB RAM

Look up Paged Address Extensions (PAE). Memory paging has been
supported in 32-bit x86 systems for years. I expect it was used in
database servers.

You probably mean Physical Address Extension. Paging is used by all x86
operating systems that are more or less widely in use these days.

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