X86

x86 is a term used to describe a CPU instruction set compatible with the Intel 8086 and its successors, including the Pentium and others made by Intel and other companies. This is the CPU architecture used in most desktop and laptop computers.  Many 21st century workstations and servers also use x86 processors. In 1985, the original 16 bit x86 architecture was extended to 32 bits with the introduction of the i386 processor. It was extended again to 64 bits in 2003 with the introduction of the AMD Opteron processor. 

Intel adopted the 64-bit computing bit architecture in 2004 with the later versions of the Prescott Pentium 4.  The different versions are backward-compatible, meaning that a 32-bit x86 CPU can run a 32-bit or 16-bit operating system, and a 64-bit x86 CPU can run a 16, 32, or 64-bit operating system.  All x86 CPUs (with the rare exception of some Intel CPUs used in embedded systems) start in 16-bit real mode. A modern operating system (or sometimes the bootloader) switches the CPU into 32-bit protected mode or 64-bit long mode before booting the kernel.

 List of x86 CPUs 
 16-bit 
 Intel 8086
 Intel 8088
 80186
 Intel 80286

 32-bit Intel 
 i386 (80386)
 i486 (80486)
 Pentium
 Pentium Pro
 Pentium 2 (or II)
 Pentium 3 (or III)
 Older versions of the Pentium 4
 Pentium M
 Intel Core
 Older versions of the Xeon processor 
 Mobile versions of Intel Atom
 Older versions of Celeron processors 

 64-bit Intel 
 Newer Prescott Pentium 4
 Pentium D
 Core 2
 Intel Core:
 i3
 i5
 i7 and i9
 Newer Atom
 Pentium dual core
 Newer Celeron
 Newer Xeon

 32-bit AMD 
 AMD386
 AMD486
 AMD586
 Am5x86-P75 (actually a 486 CPU)
 K5
 K6/K6-II/K6-III
 Athlon
 Athlon XP
 Duron
 Sempron
 Geode

 64-bit AMD 
 Opteron
 Athlon 64
 Phenom
 Phenom 2
 FX
 Sempron
 APU A4/A6/A8/A10/A12
 APU Athlon
 APU Sempron
 Ryzen
Epyc

 Others 
 Cyrix 386/486S/DLC, 5x86, 6x86, MII, MIII (32-bit)
 IDT Winchip (32-bit)
 Rise (32-bit)
 NxGen (32-bit)
 Via C3 and C7 (32-bit)
 Via Nano (64-bit)

 x86 Operating Systems 
 x86-only 
 MS-DOS, IBM PC-DOS, and FreeDOS
 XENIX, SCO OpenServer, and SCO UNIXWare
 Novell NetWare
 ReactOS
 DragonFlyBSD
 Originated on x86 
 Microsoft Windows
 Linux
 FreeBSD, NetBSD, and OpenBSD
 OS/2
 Ported to x86 
 macOS
 Solaris

 References 

 Other websites 
 X86 -Citizendium

Category:Intel processors