Linux User Group HOWTO: Introduction

Linux is a freely-distributable implementation of Unix for personal computers, servers, workstations, PDAs, and embedded systems. It was developed on the i386 and now supports a huge range of processors from tiny to colossal:

Diverse PDA / embedded / microcontroller / router devices:
- Advanced RISC Machines, Ltd. ARM family (StrongARM SA-1110, XScale, ARM6, ARM7, ARM2, ARM250, ARM3i, ARM610, ARM710, ARM720T, and ARM920T)
- Analog Devices, Inc.'s Blackfin DSP
- Axis Communications ETRAX series ("CRIS" = Code Reduced Instruction Set RISC architecture)
- Elan SC520 and SC300
- Fujitsu FR-V
- Hitachi H8 series
- Intel i960
- Intel IA32-compatibles (Cyrix MediaGX, STMicroelectronics STPC, ZF Micro ZFx86)
- Matsushita AM3x
- MIPS-compatibles (Toshiba TMPRxxxx / TXnnnn, NEC VR series, Realtek 8181)
- Motorola 680x0-based machines (Motorola VMEbus boards, ISICAD Prisma machines, and Motorola Dragonball & ColdFire CPUs, and Cisco 2500/3000/4000 series routers)
- Motorola embedded PowerPC (including MPC / PowerQUICC I, II, III families)
- NEC V850E
- Renesas Technology (formerly Hitachi) SH3/SH4 (SuperH: link1 link2)
- Samsung CalmRISC
- Texas Instruments's DM64x and C54x DSP families
Intel 8086 / 80286.
Intel IA32 family: i386, i486, Pentium, Pentium Pro, Pentium II, Pentium III, Celeron, Xeon, and Pentium IV processors, as well as IA32 clones from AMD (386DX/DXL/SL/SLC/SX, 486DX/DX2/DX4/SL/SLC/SLC2/SLC3/SX/SX2, Elan, K5, K6/K6-II/K6-III), Cyrix (386DX/DXL/SL/SLC/SX, 486DLC/DLC2/DX/DX2/DX4/SL/SLC/SLC2/SLC3/SX/SX2, Cyrix III), IDT (Winchip, Winchip 2, Winchip 2A/3), IBM (486DX/DX2/DX4/SL/SLC/SLC2/SLC3/SX/SX2), NexGen (Nx586), Transmeta (Crusoe), TI (486DLC/DLC2), UMC (486SX-S, U5D/U5S), VIA (C3 Ezra "CentaurHauls", C3-2 "Nehemiah"), and others.
Intel/HP IA64: Trillian, Itanium, Itanium2/McKinley
x86-64 x86-64 family including AMD Hammer/Opteron/K8/Athlon64 and Intel Prescott/Nocona/Potomac
Motorola 68020-68040 series (with MMU): m68k Mac, Amiga, Atari ST/TT/Medusa/Falcon, HP/Apollo Domain, HP9000/300, sun3, and Sinclair Q40.
Motorola/IBM PowerPC family: Most PowerMac (including G3/G4/G5) / CHRP / PReP / POP, Amiga PowerUP System, and IBM PPC64 (AS/400, RS/6000, iSeries, pSeries, PowerMac G5).
MIPS: most SGI, Cobalt Qube, DECStation, Sony PlayStation2, and many others
DEC Alpha
HP PA-RISC
SPARC International SPARC32 / SPARC64
Digital VAX minicomputers and MicroVAXen
Mainframes: IBM S/390 models G5 and G6 / zSeries models z800, z890, z900, and z990 and Fujitsu AP1000+ (SuperSPARC cluster)

Note that some items listed were probably one-time forks, little or not at all maintained since creation. On some of the rarer architectures, NetBSD may be more practical. (Soon, the Debian GNU/NetBSD port should be solid enough to serve as a compromise option, furnishing Linux userspace code on the highly portable NetBSD kernel.)

If seriously interested in the subject of Linux ports, please see also Xose Vazquez Perez's Linux ports page and Jerome Pinot's Linux architectures list, if only because hardware support is more complex than just generic CPU functionality, encompassing support for myriad bus variations and other subtle hardware issues (especially for Linux PDA / embedded / microcontroller / router ports). The above list aims mostly to generally illustrate the breadth of Linux's reach.