This document compares three distributed operating systems: Amoeba, Mach, and Chorus. Amoeba was designed for distributed systems and uses a pool processor execution model, automatic load balancing, and automatic file replication. Mach was designed for single CPU/multiprocessors and provides extensive multiprocessor support. Chorus is a microkernel-based real-time operating system that is optimized for the local case and provides asynchronous communication. The document outlines key differences between the three operating systems in areas such as architecture, communication methods, memory management, and UNIX compatibility.

1. Comparison of Amoeba, Mach and
Chorus
Presented By
Er. Shiva K. Shrestha (15957)
DOS, ME Computer
Nepal College of Information Technology

2. Amoeba DOS
 Times Sharing DOS
 Based on Microkernel
 Execution Model: Pool Processor
 Automatic Load Balancing
 Automatic File Replication
 Object Based DSM Used
 Main Objectives:
 Distribution, Parallelism, Transparency, Performance
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3. Amoeba System
Architecture
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4. Amoeba Microkernel
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Process management
Memory management
Communication
I/O

5. Key Concepts of Amoeba
 Microkernel
 Remote Procedure Calls (RPC)
 Threads
 FLIP
 Objects
 Capability
 Various Servers
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6. Mach DOS
 Designed for 1 CUP/Multiprocessor
 Extensive Multiprocessor Support
 Maximum No. of Kernel Calls: 153
 Memory Mapped Objects
 Integrated Memory Mgmt.
 Page Based DSM
 No Group Communication
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7. Mach Principal Abstractions
 Processes
 Threads
 Memory Objects
 Ports
 Messages
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8. Process Mgmt. in Mach
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9. Monolithic Vs. Microkernel
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10. Chorus DOS
 Microkernel Based RTOS
 Flexible Virtual Memory
Implementation
 Binary Level OS Emulation
 Async. Communication
 Page Based DSM
 Optimized for Local Case
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11. Chorus Chief Design
Features
 Dynamically Loadable Servers
 Enhancement of Unix
 Server Group & Reconfiguration
 Distributed Memory Multiprocessor
Operations
 Real-time Operations
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12. Conclusion (1)
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ITEM AMOEBA MACH CHORUS
Designed for: Distributed system 1 CPU, multiprocessor 1 CPU, multiprocessor
Execution model Pool processor Workstation Workstation
Microkernel? Yes Yes Yes
Number of kernel calls 30 153 112
Automatic load
balancing?
Yes No No
Capabilities General Only ports General
Capabilities in: User space Kernel User space
Threads managed by: Kernel Kernel Kernel
Transparent
heterogenity?
Yes No No
User-settable priorities? No Yes Yes
Multiprocessor support Minimal Extensive Moderate

13. 13
Conclusion (2)
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ITEM AMOEBA MACH CHORUS
Mapped object Segment Memory object Segment
Demand paging? No Yes Yes
Copy on write? No Yes Yes
External pagers? No Yes Yes
Distributed shared
memory
Object based Page based Page based
RPC? Yes Yes Yes
Group communication Reliable, ordered None Unreliable
Asynchronous
communication?
No Yes Yes
Intermachine messages Kernel User space/kernel Kernel
Messages address to: Process Port Port
UNIX emulation Source Binary Binary
UNIX compatibility POSIX (partial) BSD System V
Single-server UNIX? No Yes No
Multiserver UNIX? Yes No Yes
Optimized for: Remote case Local case Local case
Automatic file replication? Yes No No

14. Questions?
Thank You !
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