Here's also a good reference to the different (and to some, surprising) 
memory things going on with 32-bit stuff on Windows.
It talks about both 4GT, PAE and the /LARGEADDRESSAWARE linker option 
that some use - and the impact on system resources.
http://msdn.microsoft.com/en-us/library/aa366778.aspx

AFAIK Rom is right about those limits being per-process.

-- Janus

On 04/25/2012 09:40 PM, Rom Walton wrote:
> I'm confused. On Windows, out of the box, the largest amount of memory a
> single 32-bit program can allocate is 2GB (3GB with a special boot
> option). I believe that is even true on a 64-bit system.
>
> When your system starts to slow down, is the hard drive busy?  It sounds
> like what you are experiencing is paging related.
>
> ----- Rom
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Robert Miles
> Sent: Sunday, April 22, 2012 5:36 PM
> To: [email protected]
> Subject: [boinc_dev] 32-bit workunits under 64-bit Windows
>
> I've found that my computer tends to slow down user response quite a bit
> as the total memory used by 32-bit workunits and other 32-bit programs
> approaches 3.5 GB, as I'd expect if all 32-bit programs must fit within
> a single 4 GB memoryspace even though the computer has 8 GB of memory
> installed.  Could you check if this is actually what's happening,
> especially on 64-bit versions of Windows with the lower limits on the
> total amount of memory they can use?  If so, can you find a way to give
> each 32-bit workunit a separate 4 GB memoryspace, even if some of it is
> shared with other workunits?
>
> Another possibility is that the portions of the SysWOW64 software needed
> to run 32-bit programs is similar in size to the programs that need it,
> and therefore you should consider counting SysWOW64 software against the
> memory limit allowed for BOINC.  Or just count 32-bit workunits twice
> against the limit, but 64-bit workunits only once.  Or even allow
> setting the limit for 32-bit BOINC software and workunits to be lower
> than the total amount of memory BOINC can use.
>
> I'm using 64-bit Windows Vista Home Premium SP2 on that computer.  I
> haven't found any way to check which if either of the above
> possibilities is correct.  Currently using BOINC 7.0.25, but I have seen
> the same problem on earlier versions back to at least some of the 6.12.*
> versions.
>
> This may be a good reason for the more memory-hungry BOINC projects to
> start offering 64-bit applications, even if those 64-bit versions offer
> no performance improvements over the 32-bit versions.
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