[R-SIG-Mac] Just a thought on FAT packages

Bill Northcott w.northcott at unsw.edu.au
Tue Feb 26 04:44:24 CET 2008

I notice that the FAT MacOS X binaries being built at the moment are  
all 4 way fat.

When a fat executable is launched, it will run as 64 bit, on a Mac  
with G5 or Core2Duo processors.  There is no way of overriding this  

On a Core2Duo machine this is good because the x86_64 ISA is a  
considerable improvement on the old i386 one, and all applications  
will generally run faster on this architecture in 64 bit.  However, on  
the G5 the ISAs are the same for both 32 and 64 bit, only the pointer  
size changes.  So that 64 bit actually runs more slowly.  The only use  
for ppc64 is for programs that need very large memory spaces on G5  
machines with at least 3GB of DRAM.  I expect the sort of power users  
who run such code and can afford large amounts of DRAM have upgraded  
to a Mac Pro already.

In short, I can see very little demand for ppc64 and including it just  
reduces performance for those running G5 Macs.

Hence my suggestion to make Universal Binaries 3 way fat i386, x86_64  
and ppc.

Just a thought

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