XINU

Xinu Is Not Unix (Xinu, a recursive acronym), is an operating system for embedded systems, originally developed by Douglas Comer for educational use at Purdue University in the 1980s. The name is both recursive, and is Unix spelled backwards. It has been ported to many hardware platforms, including the DEC PDP-11 and VAX systems, Motorola 68k (Sun-2 and Sun-3 workstations, AT&T UNIX PC, MECB), Intel x86, PowerPC G3, MIPS, ARM architecture and AVR (atmega328p/Arduino). Xinu was also used for some models of Lexmark printers. Despite its name suggesting some similarity to Unix, Xinu is a different type of operating system, written with no knowledge of the Unix source code, or compatibility goals. It uses different abstractions, and system calls, some with names matching those of Unix, but different semantics. Xinu first ran on the LSI-11 platform. A Motorola 68000 port was done by Derrick Burns in 1984. A VAX port was done in 1986 by Comer and Tom Stonecypher, an IBM PC compatible port in 1988 by Comer and Timothy Fossum, a second Motorola 68000 (Sun 3) port circa 1988 by Shawn Ostermann and Steve Chapin, a Macintosh platform port in 1989 by Comer and Steven Munson, an Intel 80486 version by John Lin in 1995, a SPARC port by Jim Griffioen, and a PowerPC port in 2005 and MIPS port of Embedded Xinu in 2006 by Dennis Brylow. Dennis Brylow at Marquette University has ported Xinu to both the PowerPC and MIPSEL processor architectures. Porting Xinu to reduced instruction set computing (RISC) architectures greatly simplified its implementation, increasing its ability to be used as a tool for teaching and research. MIPSEL was chosen as a target architecture due to the proliferation of the MIPSEL-based WRT54GL router and the cool incentive that motivates some students to become involved in projects. The first embedded Xinu systems laboratory based on the WRT54GL router was developed at Marquette University. In collaboration with the Marquette Xinu team, an embedded Xinu laboratory was formed at the University of Mississippi, laying the groundwork for further work on developing a Virtual Xinu Laboratory.