Re: [R] Does R work in 64 bit on apple G5

From: Bill Northcott <w.northcott_at_unsw.edu.au>
Date: Fri 25 Mar 2005 - 13:36:42 EST

On 24/03/2005, at 10:10 PM, David Ruau wrote:
> I am working with R on 2xG5 1.8Ghz from Apple under 10.3.8
> The G5 chip is 64 bits but does R run in 64 bit or 32 under OS X?
> How can know?
> I think it run in 32 bits... but not sure...
>
It is not possible to build and run 64bit apps in MacOS X under 10.3.x.   The problem is not just the compiler. For a workable 64 bit app you also need 64bit system libraries libm etc. As a matter of interest the current kernel is 64 bit and can manage large continuous memory spaces.   However, application memory partitions are limited to 2GB each.

MacOS X 10.4 (Tiger) will have 'fat' (64/32 bit) system libraries and it will be possible to build 64 bit apps. However, Cocoa, Carbon and all the GUI stuff will remain 32 bit, because making it 64 bit would slow performance and increase memory footprint with no user benefit. You can find the full story at:
http://developer.apple.com/macosx/tiger/64bit.html

What benefit do you think you are going to get from running 64 bit? In general there will be a performance penalty and unless you need an application memory space larger than 2GB there is no benefit. Processor arithmetic is unchanged between 32 and 64 bit modes.

Bill Northcott



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