What is X86?
{{more sources|date=June 2022}} {{lowercase}} '''x86''' is a term used to describe a [[Central processing unit|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 [[workstation]]s and [[server]]s 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-bit computing|64 bits]] in 2003 with the introduction of the [[Advanced Micro Devices|AMD]] Opteron processor.<ref>{{Cite web|last=Kay|first=Russell|date=2004-04-12|title=64-Bit CPUs|url=https://www.computerworld.com/article/2564239/64-bit-cpus.html|access-date=2022-05-27|website=Computerworld|language=en}}</ref> 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 computing|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 [[booting|bootloader]]) switches the CPU into [[32-bit computing|32-bit]] protected mode or 64-bit long mode before booting the [[Kernel (computer science)|kernel]]. == List of x86 CPUs == === 16-bit === * [[Intel 8086|8086]] * 8088 * 80186 * 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 * Core * Older Xeon * Mobile versions of [[Intel Atom]] * Older Celeron === 64-bit Intel === * Newer Prescott Pentium 4 * Pentium D * Core 2 * Core i3, i5, i7, and i9 * Newer Atom * Pentium dual core * Newer Celeron * Newer Xeon === 32-bit AMD === * AMD386 * AMD4