An Introduction to Amoeba
Andrew S. Tanenbaum
Dept. of Mathematics and Computer Science
De Boelelaan 1081
1081 HV Amsterdam, The Netherlands
Sape J. Mullender
Centrum voor Wiskunde en Informatica
1098 SJ Amsterdam, The Netherlands
As the 1990s take hold, it is increasingly clear that computer operating systems
designed for single processor systems back in the 1970s and 1980s will no longer be
appropriate for the needs of the new decade. UNIX? is now almost 20 years old. Although
it has gotten much bigger over the years, the basic ideas have not really changed since it
was created in the early 1970s. MS-DOS, although not quite as old, is in many ways even
less appropriate than UNIX for the powerful computer systems of the 1990s. Perhaps it is
time to start over fresh with something new. In this collection of papers we describe the
Amoeba distributed operating system, which has been designed and implemented with the
technology of the 1990s in mind.
What are the key characteristics of computing now and in the future? We are convinced that two factors will dominate the next decade:
d The need for physically distributed hardware
d The need for logically centralized software
Let us now discuss these in turn.
First, computers are becoming cheaper at an enormous rate. In the 1970s, it was normal for many people to share a single mainframe or minicomputer by running a timesharing system on it. Each user had a terminal with which to access the computer. The ratio of computers to people was very low, often 20 or 50 or even 100 people per machine.
In the 1980s, the personal computer and personal workstation became popular. By the end of the decade, many universities and companies operated using a model in which each person had his or her own machine, all connected by a local area network. The ratio of computers to people became approximately 1 to 1, as many machines as people.
In the 1990s, hardware prices will continue will continue to drop dramatically. We will soon come to a situation in which it is economically feasible to have 20 or 50 or even 100 computers per person. Clearly the current model of giving each person a personal computer or workstation breaks down under these conditions. Nevertheless, the availability of large numbers of powerful single-chip processors is a given. Any system for the
? UNIX is a Registered Trademark of AT&T Bell Laboratories.