Title: Minix - Early Notes

Author: Martin Moene

Date: 28 June 2010 08:59:00 +01:00 or Mon, 28 June 2010 08:59:00 +01:00

Summary: 

Body: 

MINIX - a contraction of MINIature and unIX. What are your expectations? Perhaps it will be useful to begin with a description of what you get, and then assess its immediate usefulness.

The basic system consists of the documentation (Operating Systems; Design & Implementation. By Andrew S. Tanenbaum. Publisher: Prentice-Hall International. ISBN: 0-13-637331-3) and eight disks (5 1/4" 360k). One of these is for booting, and the rest contain various parts of the system. There are several options for different styles of machine (256k, floppy only, etc.)

The system, once running, has the kernel in memory, a ram disc (\tmp) and is a complete equivalent to Unix System 3, Version 7. This version was widely regarded as one of the best stages in development. The Bourne shell is also provided.

Questions Arising

Q. What would I use it for?

A. As a (very) cheap startup and development system for Unix programming

Q. How good is it?

A. Excellent; known bugs are minimal - we are collecting these, but none to start with. Depending on your background, Minix will or will not be a culture shock!

Q. How much does it cost?

A. Less than œ100 for the book and disks. This translates as less than œ600 for complete working Unix-style system on a PC clone. The book is, of course, available separately too.

Q. What is the legal situation?

A. To quote the code listings for Minix....

"Copyright (C) 1987 by Prentice-Hall Inc. Permission is hereby granted to private individuals and educational institutions to modify and redistribute the binary and source parts of the system to other private individuals and educational establishments for educational and research purposes. For corporate or professional use, permission from Prentice-Hall is required. In general, such permission will be granted, subject to a few conditions"

In general, additions will probably be welcome, casual abuse will not. The source code for the compiler (constructed using the Amsterdam Compiler Kit) is not available from Prentice-Hall, but from:

Transmediair Utrecht BV Melkweg 3 3721 RG Bilthoven Holland

Tel.: (30) 78 18 20

Implementation Details

This section and the next are deliberately kept short, because it is still very early in the author's understanding of both the system itself and the actual implementation.

The Minix kernel is fundamentally different from a normal Unix kernel. It is much smaller and major subsystems are now implemented as such (eg. filing system). In relation to the PC (IBM PC, XT or clone) the Bios is not used at all. This is because the Bios supplied for these machines is not interrupt driven - tasks run to completion even if the rest of the system is hanging. Obviously this is not viable in a multi-tasking, multi-user environment. Hence all the device drivers control their hardware directly - screen, floppy, etc.

The system should run without too much trouble on an ordinary IBM PC with or without a hard disk. For an AT, the memory management facilities of the '286 are used (good news!) and quite reasonable multi-tasking with inter-task protection is a welcome feature. As far as is known, no special development has been made for '386 systems - the scale of this is not yet properly assessed. Please write in if this aspect is of interest to you.

Mention has been made of an implementation for the Atari ST, but details are not yet known.

Please also write in if your interest is in real-time systems, as well as Unix or others; the IEEE Posix standard is becoming a reality and I consider the development of code in relation to this the highest priority at present. There are also some major implications for the Intel RMK ('386)

Finally....

A realistic note - getting this system running on your PC may take quite a while and does require a degree of commitment. Particularly, at present, hard disk interfaces are regarded as "difficult". Do please try and report difficulties (and solutions!) as you encounter them.

Good Luck!.....

Availability

Minix is available in a number of forms:

• a set of diskettes for the IBM PC set of diskettes for the IBM PC (or true compatible) with 640k RAM. Consists of the bootable system and the complete sources (including a number of utilities, but not the C compiler sources - details of how to obtain these are mentioned elsewhere in this article). Can be used with 512k, but program sizes will have to be adjusted.ISBN: 0-13-583873-8
  
  
• a set of diskettes for 256k IBM PCs. As above, but the C compiler executable is not included. ISBN: 0-13-583881-9
  
  
• a set of diskettes for 512k IBM PC/ATs. Supplied on 1.2M disks, otherwise identical to version for 640k PC (except RAM disk is slightly smaller).ISBN: 0-13-583865-7
  
  
• a nine-track, industry standard 1600 bpi magnetic tape in Unix "tar"format. Contains all the sources, an IBM PC simulator, libraries, and programs to enable the file system to work on the VAX or other Unix minis.Ports to other systems should not be too difficult, as the file system and test programs are in C. ISBN: 0-13-583899-1

Any correspondence regarding Minix should be addressed to Don (who has kindly offered to be the official Minix coordinator within the group):

Don Forbes
35 Upland Road
South Croydon
Surrey
CR2 6RE
Tel.: 01 688 5794

Notes: 

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