Difference between x86 x32 and x64 architectures

Question

Please explain the difference between x86  x32 and x64  Its a bit confusing when it comes to x86 and x32 because most of the time 32-bit programs run on x86

User · Accepted Answer

x86 refers to the Intel processor architecture that was used in PCs. Model numbers were 8088 (8 bit bus version of 8086 and used in the first IBM PC), 8086, 286, 386, 486. After which they switched to names instead of numbers to stop AMD from copying the processor names. Pentium etc, never a Hexium :).

x64 is the architecture name for the extensions to the x86 instruction set that enable 64-bit code. Invented by AMD and later copied by Intel when they couldn't get their own 64-bit arch to be competitive, Itanium didn't fare well. Other names for it are x86_64, AMD's original name and commonly used in open source tools. And amd64, AMD's next name and commonly used in Microsoft tools. Intel's own names for it (EM64T and "Intel 64") never caught on.

x32 is a fuzzy term that's not associated with hardware. It tends to be used to mean "32-bit" or "32-bit pointer architecture", Linux has an ABI by that name.

User · Answer

Hans and DarkDust answer covered i386 i686 and amd64 x86 64  so there s no sense in revisiting them  This answer will focus on X32  and provide some info learned after a X32 port   x32 is an ABI for amd64 x86 64 CPUs using 32-bit integers  longs and pointers  The idea is to combine the smaller memory and cache footprint from 32-bit data types with the larger register set of x86 64   Reference  Debian X32 Port page    x32 can provide up to about 30  reduction in memory usage and up to about 40  increase in speed  The use cases for the architecture are    vserver hosting  memory bound  netbooks tablets  low memory  performance  scientific tasks  performance     x32 is a somewhat recent addition  It requires kernel support  3 4 and above   distro support  see below   libc support  2 11 or above   and GCC 4 8 and above  improved address size prefix support    For distros  it was made available in Ubuntu 13 04 or Fedora 17  Kernel support only required pointer to be in the range from 0x00000000 to 0xffffffff  From the System V Application Binary Interface  AMD64  With LP64 and ILP32 Programming Models   Section 10 4  p  132  its the only sentence       10 4 Kernel Support   Kernel should limit stack and addresses returned from system calls between 0x00000000 to 0xffffffff    When booting a kernel with the support  you must use syscall x32 y option  When building a kernel  you must include the CONFIG X86 X32 y option   Reference  Debian X32 Port page and X32 System V Application Binary Interface      Here is some of what I have learned through a recent port after the Debian folks reported a few bugs on us after testing    the system is a lot like X86 the preprocessor defines   x86 64    and friends  and   ILP32    but not   i386     i686    and friends  you cannot use   ILP32   alone because it shows up unexpectedly under Clang and Sun Studio when interacting with the stack  you must use the 64-bit instructions pushq and popq once a register is populated configured from 32-bit data types  you can perform the 64-bit operations on them  like adcq be careful of the 0-extension that occurs on the upper 32-bits    If you are looking for a test platform  then you can use Debian 8 or above  Their wiki page at Debian X32 Port has all the information  The 3-second tour   1  enable X32 in the kernel at boot   2  use debootstrap to install the X32 chroot environment  and  3  chroot debian-x32 to enter into the environment and test your software

User · Answer

x86 means Intel 80x86 compatible  This used to include the 8086  a 16-bit only processor  Nowadays it roughly means any CPU with a 32-bit Intel compatible instruction set  usually anything from Pentium onwards   Never read x32 being used   x64 means a CPU that is x86 compatible but has a 64-bit mode as well  most often the 64-bit instruction set as introduced by AMD is meant  Intel s idea of a 64-bit mode was totally stupid and luckily Intel admitted that and is now using AMDs variant    So most of the time you can simplify it this way  x86 is Intel compatible in 32-bit mode  x64 is Intel compatible in 64-bit mode

User · Answer

As the 64bit version is an x86 architecture and was accordingly first called x86-64  that would be the most appropriate name  IMO  Also  x32 is a thing  as mentioned before       x64     however  is not a continuation of that  so is  theoretically  missleading  even though many people will know what you are talking about  and should thus only be recognised as a marketing thing  not an    official    architecture  again  IMO   obviously  others disagree

[x86] Difference between x86, x32, and x64 architectures?

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