View source for Mach

{{Infobox OS 
| image = Mach 2.5 with Lites on NetBSD.png
| caption = Logging into a Mach/Lites/NetBSD system
| name = Mach
| creator = CMU
| current version = 3.0 (1994)
| year introduced = 1985
| type = Multitasking, multiuser
| architecture = [[m68k]], [[i386]], [[POWER]], [[HPPA]], [[Sparc]]
}}

Mach was the [[microkernel]] from CMU that popularized the microkernel craze of the late 1980's and into the 1990's.  While seen as a dead end effort, it did at the time bring in many new things to the aging [[UNIX|Unix]] [[kernel]]. Mach, based loosely on [[BSD]] was a low level kernel adding [[thread]]s insteads of forked [[process]]es, and had the ability to run on SMP hardware. BSD was then ported back as a user process on top of the Mach micro kernel.

== Archived Releases ==

=== CMU ===

==== 1.x ====
During the original development started at CMU, using various accent technologies and 4.3BSD as a starting point.  There is 2 partial trees for these releases made in 1986.  I'm assuming these are some version 1.x thing  Both of these releases are on Kirk's DVD set.

==== 2.x ====
There is currently 2 versions saved of the '2.5' variation, both were found on the CSRG CD-ROM set.
* mk35
* X147

==== 3.x ====
Starting with 3.0 the 4.3BSD kernel was removed from the source making this a 'pure' Microkernel.  So far the following versions have been saved:

* mk42
* mk78
* mk80
* mk82
* mk83
* mk83a
* mk84

=== Utah ===
After the winding down on Mach research at CMU, the University of Utah picked up Mach and made releases as Mach4.  Known releases are:

* UK02p21
* UK22

=== OS/F ===
The OS/F group made various releases based on the Utah versions.  Many were encumbered, however I have managed to track back a few releases:

* MK6.1
* [https://web.archive.org/web/19970606230508/https://www.osf.org/RI/PubProjPgs/MK72.htm MK7.2]
* [https://web.archive.org/web/19971016172524/http://www.opengroup.org/RI/PubProjPgs/MK73.htm MK7.3]



== Mach Operating Systems ==

Some of the [[operating system]]s that used Mach were [[NeXTSTEP]]/[[OPENSTEP]], [[Mach386]] & [[OSF/1]].  The [[GNU Hurd]] project also used Mach at one point before abandoning it for [[L4]].

The [[GNU]] project had taken a version of Mach, and used the GNU license to 'gnu-ify' mach and produce GNUMach.
While [[Windows NT]] may share design ideas with Mach, it is NOT a derived Mach microkernel.

== Servers ==

Mach could run various '[[server]]' programs that would then provide an operating system personality to the user.

=== BSDSS ===

4.4 BSD subsystem. It was pulled at the start of the lawsuit 

=== BNR2SS ===

BSD Net/2 subsystem 


=== Lites ===

One of the more popular servers was Lites.  It was a BSD based personality that could then run early versions of NetBSD & FreeBSD.

There was also a msdos subsystem

== Criticism ==

Mach was seen as unnecesary as its main idea of running multiple servers hardly ever happened.  Most projects based on Mach only ran a single server. Also every time a program made a [[system call]] it had to transition through the kernel to talk to the 'server' process, which had to go thru Mach again to do whatever it was, then back to the server, then thru Mach again to talk to the program.  The overhead of the system call was was significant, and a way was never developed to bring the LPC calls down to something comparable to an older monolithic style OS.  This is why XNU (the Nextstep/Openstep/Darwin/OSX kernel) used Mach as a [[library]] rather then as a full blown microkernel.

The rise of Linux also showed that a re-structured monolithic kernel could not only scale on SMP hardware, but could remain portable.

== Getting it to run ==

Installing Mach on the PC is not a task for the timid.  It is VERY involved and difficult.  I have decided to provide an image [http://vpsland.superglobalmegacorp.com/install/MachUK22-lites-nat.zip here].  I may document the install later, but it is extremly complex.

{{semi-stub}}

[[Category: Operating Systems]]