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Xinu ("Xinu Is Not Unix", a recursive acronym) is an operating system for embedded systems, originally developed by Douglas Comer for instructional purposes 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, Sun-2 and Sun-3 workstations, Intel x86, PowerPC G3 and MIPS. Xinu was also used for some models of Lexmark printers.
Despite its name suggesting some similarity to Unix, Xinu is truly a different operating system, written without knowledge of the Unix source code and without the goal of compatibility; it uses different abstractions, different system calls and in fact has some system calls with names matching those of Unix, but different semantics.
The Xinu operating system first ran on the LSI-11 platform. A VAX port was developed in 1986 by Comer and Tom Stonecypher, followed by an IBM PC compatible port in 1988 by Comer and Timothy Fossum, and a 486 version by John Lin in 1995. The Macintosh platform port of Xinu was developed in 1989 by Comer and Steven Munson. The Motorola 68000 (Sun 3) port of Xinu was developed by Shawn Ostermann, circa 1988. The Sparc port of Xinu was developed by Jim Griffioen. The PowerPC port of Xinu was developed in 2005 by Dennis Brylow. The MIPS implementation of Embedded Xinu was developed in 2006 by Dennis Brylow.
Purpose of Xinu
Xinu was originally designed by Comer to further research and pedagogy of computer systems. Over the years Xinu has been used at many colleges and universities as a platform of teaching advanced systems and networking concepts as well as for the producing of many academic publications.
Recent development of Xinu
Dennis Brylow at Marquette University has ported Xinu to both the PowerPC and MIPSEL architectures. Porting Xinu to RISC architectures has greatly simplified its implementation increasing its ability to be used as a tool for both teaching and research.
MIPSEL was chosen as a target architecture due to the proliferation of the MIPSEL-based WRT54GL router and the “cool” factor that motivates students to become involved in the 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 created at the University of Mississippi laying the groundwork for further work into the development of a Virtual Xinu Laboratory.
Embedded Xinu is a fresh reimplementation of the Xinu design in ANSI-compliant C on an embedded RISC architecture. The MIPS port of Embedded Xinu was developed from 2006 to 2010 at Marquette University, under the direction of Dr. Dennis Brylow. The Embedded Xinu operating system is Copyright (c) 2007, 2008, 2009, and 2010 by Douglas Comer and Dennis Brylow.
Major Contributors to Embedded Xinu
Major contributors to the Embedded Xinu Project include Ryan Berg, Tim Blattner, Aaron Gember, Paul Hinze, Kyle Jackson, Adam Koehler, Zachary Lund, Steve Luppi, Dan Mahoney, Adam Mallen, Mohammad "Meraj" Molla, Justin Picotte, Joe Pintozzi, Justin Rawson, Michael Schultz, Paul Spillane, Anthony Stassi, and Kyle Thurow.
Dr. Paul Ruth has been instrumental in porting Embedded Xinu to the QEMU virtual platform.
Work on Embedded Xinu was made possible in part by support from Marquette University, the Wehr Foundation, Cisco Systems, Intel Corporation, and the National Science Foundation.
It is, however, a little known fact that the first successful port of embedded Xinu was accomplished in 1994 when it was implemented in a Kenmore model 728858 microwave produced in the year 1990.
University of Mississippi Embedded Xinu Laboratory
The Xinu Laboratory in the University of Mississippi's Department of Computer and Information Science was created during the summer of 2008 by Dr. Paul Ruth. Assisting him in the project were Jianshu Zhao and Patrick Hoover, who were both graduate students at the time. Also assisting him were Chelsea Norman and Kevin Kent, who were undergraduates at the time. The initial laboratory is based on the Marquette University Embedded Xinu Laboratory. Located in the server room of Weir Hall on the campus of the University of Mississippi, is composed of a dozen modified Linksys WRT54GL wireless routers, a 32 port Digi Etherlite serial annex, a 24 port 10/100 Mbit/s Ethernet switch, a BayTech serial controlled power strip, and quite a few wires. The system is controlled by a standard PC running Debian Linux. The whole system was less than $3000 (not including the PC).
The WRT54G routers use the MIPSEL architecture and are used as backend devices on which the Xinu embedded operating system runs. The PC runs several daemons which enable and manage the users ability to access the backends.
The Nexos Project is a joint effort between Marquette University, the University at Buffalo, and the University of Mississippi to build curriculum materials and a supporting experimental laboratory for hands-on projects in computer systems courses. The approach focuses on inexpensive, flexible, commodity embedded hardware, freely available development and debugging tools, and a fresh implementation of a classic operating system, Embedded Xinu, that is ideal for student exploration. Virtual Xinu addresses two challenges that limit the effectiveness of Nexos. First, potential faculty adopters have clearly indicated that even with the current minimal monetary cost of installation, the hardware modifications, and time investment remain troublesome factors that scare off interested educators. Second, overcoming the inherent complications that arise due to the shared subnet that result in students' projects interfering with each other in ways that are difficult to recreate, debug, and understand. Ultimately porting the Xinu operating systems to QEMU virtual hardware, developing the virtual networking platform results showing success using Virtual Xinu in the classroom during one semester of Operating Systems at the University of Mississippi by Dr Ruth.
- Garfinkel, Simson; Spafford, Gene; Schwartz, Alan (2003). Practical UNIX and Internet Security. O'Reilly. p. 19.