---
title: "Characteristics of multiprocessors"
subject: "Computer Organization and Architecture"
chapter: 8
key: "semester_5/computer_organization_and_architecture:multiprocessor-characteristics"
source: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/multiprocessor-characteristics
site: BCT Engineering
---

# Characteristics of multiprocessors

Computer Organization and Architecture · Chapter 8: Multiprocessors

- Asked in: 2075 Asoj, 4 marks; 2070 Chaitra, 4 marks; 2068 Chaitra, 4 marks (asked 3 times)
- Video: [Characteristics of Multiprocessors In Computer Organization Architecture](https://www.youtube.com/watch?v=LO6Ta6kNbU0) — Sudhakar Atchala
- 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/multiprocessor-characteristics
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_organization_and_architecture/chapter-8

## Question

Define multiprocessor and explain its characteristics.

## Short answer

A multiprocessor is a system with two or more CPUs sharing memory and I/O under a single OS, enabling parallel processing. Key characteristics include shared resources, interconnection via bus/crossbar, synchronization through locks, reliability through graceful degradation, and tight or loose coupling.

## Answer

A **multiprocessor** is a computer system with two or more CPUs (processors) under one operating system, sharing memory and I/O, and cooperating to execute programs. The CPUs interact at the level of jobs, tasks, programs or instructions.

#### Characteristics
- **Two or more processors** of comparable capability, working under a common integrated OS.
- **Shared resources:** the processors share the main memory (global memory), I/O devices and the bus, in addition to their own local memory or cache.
- **Parallel processing:** several programs or parts of a program run at the same time, giving higher throughput and speed.
- **Interconnection:** processors, memories and I/O are connected by a time-shared bus, multiport memory, crossbar or multistage network.
- **Cooperation and synchronization:** processors communicate through shared memory or messages and use semaphores or locks for mutual exclusion.
- **Reliability and fault tolerance:** a failed processor can be removed while the others continue, so the system degrades gracefully.
- **Coupling:** the system may be tightly coupled (shared memory) or loosely coupled (distributed memory).

## Check yourself

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

1. What defines a multiprocessor?
   A. A network of unrelated computers
   B. One CPU with many programs
   C. A CPU with a large cache
   D. Two or more CPUs under one OS, sharing memory and I/O
   Answer: D. A multiprocessor has several processors under one OS cooperating on programs. (Key point: Definition)

2. Which resources are shared in a multiprocessor?
   A. Nothing
   B. Main memory, I/O devices and the bus
   C. Only registers
   D. Only the ALU
   Answer: B. Processors share global memory, I/O and bus, besides their own local memory or cache. (Key point: Shared resources)

3. What happens when one processor fails?
   A. The OS restarts forever
   B. It can be removed and the others continue (graceful degradation)
   C. The whole system stops
   D. All data is erased
   Answer: B. The system continues at reduced performance. (Key point: Fault tolerance)

4. What do processors use for mutual exclusion?
   A. Printers
   B. DMA
   C. Cache lines only
   D. Semaphores or locks
   Answer: D. Cooperation uses semaphores or locks. (Key point: Synchronization)

## Related in Computer Organization and Architecture

- [Tightly-coupled multiprocessor](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_organization_and_architecture%3Atightly-coupled) — Computer Organization and Architecture, chapter 8