The Mach 4 Project

Note: the Mach 4 Project is no longer active at Utah, however Mach4 is alive and well as part of the xMach project.

The goal of the Mach 4 project is to investigate some new research ideas, fix the major problems of Mach 3, and provide the base needed by the Flux project, ending up with a fast, flexible, functional kernel worthy of being called Mach version 4. We will retain compatibility with Mach 3 to as much as is practical. Slides from an overview talk concentrating on aspects of the Mach 4 kernel give some details.

It is important to note that most of our work distributed up to this point (and on the Intel x86 platform, all of it) contains little of our research. On the x86, the distributed changes have been 100% oriented to increasing Mach's ease of use and practicality in a PC environment. This emphasis is reflected in these pages. The research and development are happening, and will be available eventually.

Release Information

Latest Releases

Old Release Information

The latest Mach snapshot for the x86 is available by anonymous FTP to In general, the PA version has not yet been wholly integrated with these rather x86-specific mach4 notes or the source code-- as currently distributed, they are separate tar files. This will change!

See the "changes" sections below, the ChangeLogs in the source distribution, and the mailing list archive to find out what's new and different from CMU's version of Mach, and what is planned for the near future. We will be putting some more complete documentation in these Web pages before long.

The current snapshot is primarily based on CMU's MK83a, with a totally new GNU-style build environment and changes by Johannes Helander to support the Lites server. The hp700 support is all new vs. MK83. On the x86, we have introduced a new microkernel boot mechanism and incorporated changes from Remy Card to support Linux ext2 filesystems, and changes from Csizmazia Balazs to support MINIX filesystems. The kernel also contains some new device drivers provided by Shantanu Goel and Steve Clawson. The x86 kernel can be booted from either Linux, NetBSD, or Mach boot loaders, runs Lites with no problem, but does not incorporate any of our research work. However, that will be coming soon.

Mailing Lists

Send a message to to get on the mach4-users mailing list, which is for general questions and discussion regarding the Mach 4 project. You can get a copy of the mailing list archive from (1.3MB in November '95).

You can also read the mach4-users mailing list archive on-line either by threads or by subject.

If you would prefer to see only announcements relating to the project, send a message to to get on the mach4-announce mailing list, which is a lower-volume list for announcements only. Note that if you are on the mach4-users mailing list, you will also see everything posted to the mach4-announce list: you do not need to be on both lists at once.

Warning: There is probably a lot of slightly (or grossly) out-of-date information in these pages; it's impossible to keep them up-to-date all the time. If you find anything obviously inaccurate or out-of-date, please send us a message, preferably containing some replacement text that we can simply glue in. It'll get updated faster that way.

More Information

Related Projects

UP: Flex/Mach project
Last modified Fri Nov 3 1995