---
title: "Multiprocessor and multiprocessing"
subject: "Computer Organization and Architecture"
chapter: 8
key: "semester_5/computer_organization_and_architecture:multiprocessing-intro"
source: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/multiprocessing-intro
site: BCT Engineering
---

# Multiprocessor and multiprocessing

Computer Organization and Architecture · Chapter 8: Multiprocessors

- Asked in: 2072 Kartik, 4 marks
- Video: [COMPUTER ORGANIZATION | Part-12 | Multiprocessors & Multicomputers](https://www.youtube.com/watch?v=hrcgK9rFkSU) — Engineering Drive
- 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/multiprocessing-intro
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_organization_and_architecture/chapter-8

## Question

Explain about multiprocessor and multiprocessing in brief.

## Short answer

A multiprocessor is a system with multiple CPUs sharing memory and I/O under one OS. Multiprocessing executes tasks in parallel, increasing throughput and reliability. Systems can be tightly coupled (shared memory) or loosely coupled (message passing), connected by bus, crossbar or multistage networks.

## Answer

A **multiprocessor** is a computer system with two or more CPUs that share main memory and I/O and are controlled by one operating system. **Multiprocessing** is the use of two or more processors to execute several tasks, or parts of one task, at the same time, to raise throughput and reliability.

- Types: tightly coupled (shared memory, communication via common memory) and loosely coupled (each processor has local memory and communicates by messages).
- Processors are connected by a bus, crossbar or multistage switching network.
- Advantages: higher speed and throughput, better reliability (graceful degradation), scalability.
- Problems: memory contention, cache coherence, synchronization of processors (semaphores, TSL), and a complex operating system.
- Examples: dual-core and multi-core CPUs, SMP servers.

## Check yourself

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

1. What is multiprocessing?
   A. Only multitasking on one CPU
   B. Using one processor
   C. Using a large disk
   D. Using two or more processors to execute tasks at the same time
   Answer: D. It raises throughput and reliability. (Key point: Multiprocessing)

2. Which statement is correct?
   A. Both use shared memory only
   B. Loosely coupled uses a common memory
   C. Tightly coupled uses messages only
   D. Tightly coupled: shared memory; loosely coupled: local memory and messages
   Answer: D. Coupling depends on memory organisation. (Key point: Coupling types)

3. Which is a problem of multiprocessors?
   A. Lower throughput
   B. No scalability
   C. No OS needed
   D. Memory contention, cache coherence and synchronization
   Answer: D. These issues make the OS complex. (Key point: Problems)

## Related in other subjects

- [Distributed object versus multiprocessor architecture](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Adistributed-object-vs-multiprocessor) — Software Engineering, chapter 3
- [Multiprocessor versus client-server architecture](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Amultiprocessor-vs-client-server) — Software Engineering, chapter 3