View source for Find out if you have a 32bit or 64bit system

When [[installing software]] you usually have the choice between i386 binaries and x86_64 (also called [http://en.wikipedia.org/wiki/X64 X64]) ones. The reason for this is that there are two types of processors: 32bit processors and 64bit processors. 32 bit processors will allow you to address 2<sup>32</sup> bytes of RAM (4 GB) while 64bit processors are laid out to address 2<sup>64</sup> bytes of RAM.

The X64 architecture is the X86_32 architecture plus some extensions to stay backwards compatible. In other words, you can run 32 bit software on X64 computers.

If you have a "normal" PC it may be a 32bit one or a 64bit one. For more information, please refer to the excellent articles on wikipedia.

This article is only about X86_32 and X86_64 computers. [http://en.wikipedia.org/wiki/Itanium Itanium] computers are always based on 64bit. [http://en.wikipedia.org/wiki/IBM_POWER Power Processors] are a separate story.

In for a [[process]] to address more than 4 GB of RAM (and use the extended registers), the following conditions must be met:
* the hardware must support the 64bit extensions
* the operating system must support the 64bit extensions
* the application must be compiled to support the 64bit extensions

A 64 bit application can only run on a 64 bit operating system and a 64 bit operating system can only run on 64 bit hardware.

= Hardware =
You can find out if your hardware support the X64 extensions by looking at the lm flag of your processor:
 computer:~ # hwinfo --cpu
 01: None 00.0: 10103 CPU
   [Created at cpu.301]
   Unique ID: rdCR.j8NaKXDZtZ6
   Hardware Class: cpu
   Arch: X86-64
   Vendor: "GenuineIntel"
   Model: 6.2.3 "QEMU Virtual CPU version 0.12.3"
   Features: fpu,de,pse,tsc,msr,pae,mce,cx8,apic,sep,mtrr,pge,mca,cmov,pat,pse36,clflush,mmx,fxsr,sse,sse2,syscall,'''lm''',rep_good,nopl,pni,cx16,lahf_lm
   Clock: 2659 MHz
   BogoMips: 5319.60
   Cache: 4096 kb
   Config Status: cfg=new, avail=yes, need=no, active=unknown
 [...]

= Operating System =
On a LINUX operating system the size of the base machine can be obtained using the [[uname]] [[command]].
 uname -p

will return an appropriate string defining the processor.
x86_64 means that the machine is a 64-bit intel-style processor.
i686 means that the machine CPU is a 32-bit intel instruction set processor.

= Application =
A [[program]] that is compiled for the X64 extensions can be detected with the [[file]] [[command]]:
 # file /bin/bash
 /bin/bash: ELF 64-bit LSB shared object, '''x86-64''', version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped

= See also =
* [[find out your distribution]]