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Re: Use of large memory

  • To: mathgroup at
  • Subject: [mg50440] Re: Use of large memory
  • From: Urijah Kaplan <uak at>
  • Date: Sat, 4 Sep 2004 01:43:15 -0400 (EDT)
  • Organization: University of Pennsylvania
  • References: <ch980l$fgd$>
  • Sender: owner-wri-mathgroup at

This post is completely irrelevant, sorry to say. The question was how to 
increase the per process memory limit past 2 GB. The answer (already given 
by Vincent Virgilio) is use the the /3GB switch in Boot.ini (or the 
/USERVA switch for a precise amount. Windows 2003 only 

You confused that with the pagefile, which is something else. (It's 
essentially a place to temporarily store data on disk from RAM that hasn't 
been used in a while. Setting that to min. 4 GB is way overkill, there is 
no reason to do that. In fact, if you have enough memory you can probably 
get away with disabling the pagefile entirely, though I wouldn't recommend 

If you use a 64-bit operating system with 64 bit chips, the per process 
limit is 4GB automatically for 32 bit apps, (and of course much larger for 
64 bit apps.). 64 bit Windows (XP or 2003) won't be out for a few more 
months though, but you can get 64 bit Linux already from SUSE and perhaps 
others. You can download a preview of 64 bit XP here
if you're curious.

For more information about the /3GB switch than you will ever want to 
know, check this out

	--Urijah Kaplan

Hobbs, Sylvia (DPH) wrote:
> So the stork has just delivered a new bouncing baby Pentium
> (CONGRATULATIONS!) and its memory diapers are full (treasure these moments).
> If you haven't already tried this, then click on Control Panel, Click on
> System, Advanced, Page File Size Virtual Memory, and increase BOTH the
> Minimum Allowed AND the Maximum Allowed to the same amount = 4095 megabytes,
> this can eliminate some memory errors and also eliminates waiting around
> while the operating system thrashes between the minimum and maximum.  For
> new computers if you installed the applications yourself and have all of the
> CDs, you can remove and reinstall applications in such a way that the
> virtual memory is as close to the front of the drive as possible. When you
> reinstall, first install the barest part of the operating system, then, as
> described above, reset Minimum and Maximum memory, then reinstall all the
> other bells and whistles and other applications. If you have two physical
> drives (not logical drives where one physical drive is partitioned into two
> drives), these two physical drives have two IDE controller slots on the
> motherboard. It is best if the virtual memory - the page file system is
> handled by one disk controller on one physical drive and data files are
> handled by the other on the second physical drive. You mitigate memory
> flatulence if data crunches on a separate physical drive location from the
> virtual memory pagefile.sys. A word of caution though, if you need to listen
> to the new Beastie Boys CD or books on CD while running an application and
> if that application shares the same IDE controller as the CD, when the CD
> runs it will slow down the application. That's why some prefer one IDE
> controller for two physical hard drives and the other controller for the CD
> ROM. 
> Sylvia Hobbs
> -----Original Message-----
> From: Gerry Flanagan [mailto:flanagan at]
To: mathgroup at
> Subject: [mg50440]  Use of large memory
> I was running into memory limits for a large numerical problem in V5.0. The
> fastest fix (I thought) was to get a large amount of RAM. We purchased a
> Pentium 4 machine running XP, with 4GB of memory. I built a test function
> that progressively uses more memory and prints MemoryUsed[]. Every time I
> get to just under 2GB of memory, I get the out-of-memory error from the
> kernal. There's nothing else running, and task manager says there's plenty
> left. Has anyone found some Windows XP tweak that allows Mathematica to use
> what's available? Would this all work better in Linux?
> Gerry Flanagan

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