>>206
いやいや、そうでもないみたいよ
ttp://ktjx.blogspot.com/2009/12/mac-os-x-ruby-os.html
によると
OS付属、MacPorts、自分で入れたものでそれぞれ
ruby 1.8.7 (2008-08-11 patchlevel 72) [universal-darwin10.0]
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin10]
ruby 1.8.7 (2009-12-24 patchlevel 248) [x86_64-darwin10.2.0]
みたいになるそうだ

それぞれの実行ファイルは
% file /usr/bin/ruby
/usr/bin/ruby: Mach-O universal binary with 3 architectures
/usr/bin/ruby (for architecture x86_64): Mach-O 64-bit executable x86_64
/usr/bin/ruby (for architecture i386): Mach-O executable i386
/usr/bin/ruby (for architecture ppc7400): Mach-O executable ppc

% file /opt/local/bin/ruby
/opt/local/bin/ruby: Mach-O 64-bit executable x86_64

% file ~/local/bin/ruby
/Users/katsuji/local/bin/ruby: Mach-O 64-bit executable x86_64
なんだって