---
title: "OS configurations in multiprocessor systems"
subject: "Computer Organization and Architecture"
chapter: 8
key: "semester_5/computer_organization_and_architecture:os-multiprocessor"
source: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/os-multiprocessor
site: BCT Engineering
---

# OS configurations in multiprocessor systems

Computer Organization and Architecture · Chapter 8: Multiprocessors

- Asked in: 2074 Chaitra, 4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/os-multiprocessor
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_organization_and_architecture/chapter-8

## Question

Explain the various configurations of OS in a multiprocessor system.

## Short answer

Separate OS: each processor has its own OS and resources, simple but poor sharing. Master-slave: one processor runs the OS, others execute user programs, simple but master is a bottleneck. Symmetric (SMP): OS runs on any processor, each schedules from a common queue, best balance but complex.

## Answer

The operating system for a multiprocessor can be organised in three ways:

1. **Separate operating system (separate kernel):** each processor has its own OS and its own resources (memory, I/O). A processor is mostly independent and the processors co-operate loosely. It is simple and fault-tolerant but cannot share resources efficiently. It is suitable for loosely coupled systems.
2. **Master-slave:** one processor (the master) always runs the OS and controls the system: it schedules, performs the I/O and system calls. The other processors (slaves) execute user programs and ask the master for services. It is simple and avoids resource conflicts, but the master can be a bottleneck and its failure stops the system.
3. **Symmetric (SMP, distributed) operating system:** the OS can run on any processor, and each processor does its own scheduling from a common queue. The role of master floats. It gives the best balance and reliability, but is the most complex because of conflicts on shared tables; it needs careful locking.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. In the separate OS configuration, what does each processor have?
   A. No memory
   B. Its own OS and resources
   C. A shared OS only
   D. A master
   Answer: B. It is simple and fault-tolerant but shares resources poorly. (Key point: Separate OS)

2. What is the main weakness of master-slave?
   A. No I/O
   B. No scheduling
   C. Too many masters
   D. The master can be a bottleneck and its failure stops the system
   Answer: D. Only the master runs the OS. (Key point: Master-slave)

3. In a symmetric OS, where can the OS run?
   A. On any processor, each scheduling from a common queue
   B. Only on slave 1
   C. Only on the master
   D. On no processor
   Answer: A. The master role floats. (Key point: Symmetric OS)

4. Why is the symmetric OS most complex?
   A. It uses one CPU
   B. It cannot schedule
   C. It has no tables
   D. Conflicts on shared tables need careful locking
   Answer: D. Shared tables need locks. (Key point: Complexity)

## Related in Computer Organization and Architecture

- [Multiprocessor performance and reliability](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_organization_and_architecture%3Amultiprocessor-benefits) — Computer Organization and Architecture, chapter 8

## Related in other subjects

- [OS abstraction, extended machine, system call](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Aos-abstraction-system-call) — Operating System, chapter 1
- [Real-time system and real-time OS components](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Areal-time-os) — Software Engineering, chapter 4
- [Basic configurations of insulator string](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Ainsulator-string-configurations) — Transmission and Distribution System Design, chapter 3
- [LTI system and closed loop in modern systems](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Alti-define-cl-pronounced) — Control Systems, chapter 1