RE: [R] Amount of memory under different OS

From: Prof Brian Ripley <>
Date: Tue 05 Apr 2005 - 17:19:11 EST

On Mon, 4 Apr 2005, bogdan romocea wrote:

> You need another OS. Standard/32-bit Windows (XP, 2000 etc) can't use
> more than 4 GB of RAM. Anyway, if you try to buy a box with 16 GB of
> RAM, the seller will probably warn you about Windows and recommend a
> suitable OS.

There _are_ versions of Windows 2000 and later which can support more than 4Gb (and I hope if you buy a box with more memory you would be sold the appropriate version). If you have a 32-bit address space you cannot have more than 4Gb of addresses, physical or virtual. So some modern `32-bit' chips have segmented addressing: see e.g.

(where PAE is the scheme used on IA-32 aka ix86 chips). AFAIK the story is the same for most IA-32 OSes: each process gets a 4Gb address space and (usually) 3Gb of that is user space. R's memory usage will get cramped when the address space is tight: you probably do not want to be using 1Gb objects in a 3Gb address space (and if you need to, try R-2.1.0 beta).

The question did not mention R, and `very tough' is not at all explicit.

For large R tasks we have been recommending 64-bit OSes for quite a long time. There are 64-bit versions of Windows for AMD64/EMD64T chips, but not versions of the compilers used to build R for Windows. There are many users here of R under Linux (usually Fedora Core 3 or SuSE 9.x) on such chips.

> -----Original Message-----
> From: []
> Sent: Saturday, April 02, 2005 12:48 PM
> To:
> Subject: [R] Amount of memory under different OS
> I have a problem: I need to perform a very tough analysis, so I would
> like to buy a new computer with about 16 GB of RAM. Is it possible to
> use all this memory under Windows or have I to install other OS?

Brian D. Ripley,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Tue Apr 05 17:27:19 2005

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