Difference between Multiprocessor and Multicomputer System

Multiprocessors and multicomputer systems are forms of parallel computers. The main distinction between these systems is that a multiprocessor is a single computer that contains numerous interconnected processors with standard computing resources like memory and Input/output devices. On the other hand, the multicomputer is built by linking numerous autonomous computers via a network, and every autonomous system has its computational power.

In this article, you will learn about the difference between Multiprocessor and a Multicomputer. But before discussing the differences, you must know about Multiprocessors and Multicomputer with their advantages and disadvantages.

What is Multiprocessor?

A multiprocessor is a system that contains multiple central processing units (CPUs) that share full access to a common random access memory (RAM). The main aim of using a multiprocessor is to enhance the speed of system execution, with other goals including app matching and fault tolerance. Multiple processors may execute various tasks simultaneously. If one CPU has failed, it doesn't affect the tasks of the other processors. As a result, a multiprocessor is more dependable.

Multiprocessors are classified into two types: shared memory multiprocessors and distributed memory multiprocessors.

Shared Memory Multiprocessors

In shared memory multiprocessors, the common memory is shared by all CPUs, and the processors may communicate with each other by reading and writing to memory. It is also known as the symmetric multiprocessor system.

Distributed Memory Multiprocessor

In a distributed memory multiprocessor, every processor has its private memory. If the requested data is not available in private memory, the processor utilizes the bus to communicate with the main memory or other processors. A multiprocessor offers faster computing, higher performance, and greater fault tolerance.

Models in Multiprocessor

There are mainly three models in a multiprocessor. These are as follows:

1. UMA (Uniform Memory Access)

This model distributes physical memory uniformly among the processors, with each processor having an equal access time to all memory words.

2. NUMA (Non-Uniform Memory Access) model

It is a shared memory multiprocessor only in that the access time varies depending on the position of the memory word. The NUMA model comes in two variants. One model physically distributes shared memory to all Processing units, whereas the other model employs shared memory in a multiprocessor system.

3. COMA (Cache-Only Memory Architecture) model

This model is made up of a multiprocessor and cache memory combination. It converts distributed memory into the cache memory. It doesn't utilize the memory hierarchy, and global address space is created by aggregating all caches.

Advantages and Disadvantages of Multiprocessor

There are various advantages and disadvantages of the multiprocessor system. Some advantages and disadvantages of the multiprocessor system are as follows:

Advantages

1. As several processors share their job between one and another system, the work is completed with collaboration. It suggests that these systems are dependable.
2. When numerous processors are connected, it aids in matching the needs of an application. At the same time, a multiprocessor system saves money by eliminating the need for centralized capabilities. However, this structure allows for future expansion.
3. It aids in enhancing the authenticity of the system. A failure in any one component of a multiprocessor system has a limited impact on the rest of the system.
4. It aids in enhancing the system's cost or performance ratio.
5. There is a larger burden in a single processor system because several processes should be executed simultaneously. However, several processes are executed just a few times in a multiprocessor system. It means multiprocessor CPUs use less power than a single processor.

Disadvantages

1. It has several processors that share a memory, peripherals, and some other resources.
2. If one of the CPUs fails, the work is shared among the remaining CPUs. The negative effect will be that work will be completed quickly, and the system's performance will suffer.
3. Even while multiprocessor systems are cheaper in the long term than using several systems, they are still extremely expensive. A simple single-processor system is substantially cheaper to buy than a multiprocessor system.
4. All processors share memory in a multiprocessor system. As a result, a substantially bigger pool of memory is needed than in single-processor systems.
5. If one processor is already utilizing an Input/output device, additional processors cannot utilize the same Input/output device, resulting in deadlock.

What is a Multicomputer?

A multicomputer is a system that contains numerous processors that work together to solve an issue. Every processor has its memory, which is solely accessible by that processor. An interconnection network allows the processors to communicate with one another.

As the multicomputer can transmit messages between the processors, the task may be categorized among the CPUs to be completed. Therefore, the multicomputer may be utilized for distributed computation. A multicomputer is easier and less expensive to develop than a multiprocessor. On the other hand, programming a multicomputer is complex.

The multicomputer is the foundation of the NORMA model. NORMA is an abbreviation for "No-Remote Memory Access". It describes how numerous autonomous nodes with a processor, local memory, linked disks, and Input/Output peripherals communicate via messages rather than direct communication.

Multicomputer Generations

Multicomputer has gone via a number of unique technological stages that may be traced back through their various generations, ultimately aiming for huge parallel processing.

First generation

The first generation (1983-1987) was built with multiple microprocessors, popular static interconnection networks (hypercube-based), and software-controlled message-passing mechanisms. As a result, it provides a cost/performance ratio that eventually puts a strong challenge against the most popular versatile mainframe machines of those days from multinational giants such as HP, DEC, IBM, NCR, and others.

Second Generation

The second generation of multicomputer (1988-1992) replaced the slower software-controlled message-passing mechanism with faster microprocessors, such as RISC processors, mesh topology, enhanced interconnection networks, and hardware-supported routing algorithms (wormhole routing). As a result, global communication latency was reduced to less than 5 ps from 6000 ps, and local communication latency was reduced to 5 ps from 2000 ps, with a speed increase of about 10 times on average over its predecessors. However, this generation provided medium-grain parallelism at the processing level of tasks, processes, and subroutines to balance this computational resolution with the current communication latency to achieve adequate synchronization.

Third generation

The third generation (1993-1997) of a multicomputer is a fine-grained multicomputer with a bigger number of more advanced processors, quicker routing channels, and a medium size of private memory to every CPU, aiming for huge parallelism by studying both instruction-level parallelism and data parallelism. It offers adequate language and run-time software environment support, as has the usage of an optimizing compiler, which may automatically detect parallelism and translate source code to an acceptable parallel form that the run-time system may recognize during execution.

Features of Multicomputer

There are various features of a multicomputer. Some features of multicomputer are as follows:

1. Multicomputer programming is complex.
2. It is less expensive to develop.
3. It is simple and easy to learn.

Key differences between Multiprocessor and Multicomputer Systems

There are various key differences between Multiprocessor and Multicomputer System. Some of the key differences between the Multiprocessor and Multicomputer systems are as follows:

1. A multiprocessor is a system with multiple central processing units (CPUs) that may perform various tasks. In contrast, a multicomputer is a system having numerous processors linked via an interconnection network to complete a calculation task.
2. Programs in multiprocessor systems tend to be simpler. In contrast, programs on multicomputer systems tend to be more challenging.
3. Multiprocessors employ a dynamic network in which communication links may be reorganized by changing the system's active switching unit. In contrast, the multicomputer utilizes a static network in which the connection of switching units is fixed and defined by direct point-to-point connections.
4. A multiprocessor system requires proper communication between the processing components and memory for successful resource allocation. In contrast, no interaction between processor units or memory resources is required in a multicomputer.
5. Multiprocessors support parallel computing. In contrast, distributed computing is supported by a multicomputer.
6. A multicomputer is less difficult and less expensive to develop than a multiprocessor.
7. The microprocessor is known as a tightly coupled system. In contrast, multicomputers are referred to as loosely coupled systems.

Head-to-head comparison between Multiprocessor and Multicomputer Systems

Here, you will learn the head-to-head comparisons between the Multiprocessor and Multicomputer systems. The main differences between the Multiprocessor and Multicomputer systems are as follows:

Conclusion

The multicomputer and multiprocessor are both parallel computer types, and the multiprocessor contains multiple processing components that use shared memory. In contrast, in a multicomputer, multiple autonomous computers are linked together, and each has its own distributed memory.