mrt@MRT.MACH.CS.CMU.EDU (Mary Thompson) (11/21/90)
In respsonse to the following mail from Alan Clegg I thought I would attempt
to clairfy a few things.
I thought MACH was a clean new OS. Seems that the licence requirements for
AT&T V 3.2 are on a by-machine basis,
I would LOVE to see a good, cheap UNIX with source code, but until people get
away from the AT&T source code (BSD 4.3 as well), I don't see it happening...
Just wondering about things...
The Mach project set out to rewrite the parts of an operating system that
were interesting to us (Virtual Memory, Interprocess communications, multi-
processing support), but to retain Unix compatibility, so that the whole vast
ammount of Unix opererating system code and user programs would continue
to work with no changes. We also needed to have the same kernel run on
a variety of different architectures, partly because portability of kernels
is an interesting problem and partly because we have a lot of different machines
at CMU.
Mach 2.5 looks a lot like a 4BSD Unix system with certain key parts of the
kernel rewritten. As a result it requires a 4BSD license (which, in turn, requires
an AT&T source license) as well as whatever licenses particular vendors require
for their device drivers. Mach 2.5 is available for a variety of machines from
CMU, Mt Xinu, the OS, Encore, Omron and possibly some other vendors. It is
primarily targeted for reseach instituions who have soruce lisences and know
how to build and configure Unix systems.
Mach 3.0 set out to create a kernel operating system by putting a minimum of
functions in the kernel and having all other functions done in user space.
The Mach 3.0 pure kernel consists of virtual memory, ipc, task, thread and
scheduling primitives and currently the device drivers. Networking support,
file systems, Unix signals are now all done in user space. The Mach 3.0 kernel
is now almost license-free for the i386. Mach 3.0 does not run on as many
architectures as Mach 2.5 and the other machines types have vendor-licensed
device drivers.
The Mach 3.0 kernel by itself is just a start on a license-free Unix-style
operating system. As has currently been discussed on this b-board serveral
groups are working on getting other parts of Unix rewritten: FSF already provides
a number of utilities such as a compiler, debugger, editor and are working on
extending our POE environment. Sprite and University of Guelph are working on
filesystems. The network code is already license-free from Berkeley, but we
haven't integrated that version into Mach 3.0. Berkely is working on making
more parts of the system free. But all these projects take time and then it
will take more time to integrate everything into a coherant system. And in the
case of everyone except FSF, the organizations` first priority is doing original
research, not rewriting old operating systems or distributing software for free.
The Mach 3.0 kernel sources, POE and possbibly some user programs are nearly
ready to be distributed without requiring any licenses. The current delay is
in getting the CMU administation and lawyers to agree to some disclaimer
notice to include in the files. Understandably, the folks who are responsible
in running the University are not enthusiastic about the possibility of being
sued as the result of giving code away. Even once this obstacle is overcome,
the system is still very much under development and a copy of the sources at
any given time is subject to future changes without notice.
Mary Thompson
Project Mach Distribution Manager