This article describes the difference between symmetric and asymmetric multiprocessing. A multiprocessing system is defined as the capability of performing multiple processes simultaneously. Based on the kind of processors used, multiprocessing systems can be of the following two types.
- Asymmetric Multiprocessing
- Symmetric multiprocessing
In this article, we will be discussing the differences between Asymmetric and Symmetric multiprocessing based on several factors such as construction, memory usage, tasks performed, communication between the processors, etc.
What is Asymmetric Multiprocessing?
Asymmetric multiprocessors are defined as the type of processors involving the use of multiple processors controlled by a processor called the master processor. The processors in an asymmetric processing system operate based on a master-slave relationship.
According to this relationship, the master processor performs the task of the operating system, manages the entire data structure, programs the slave processors, and assigns tasks to the slave processors as well.
Even though all the processors of the asymmetric multiprocessing system are interconnected, no sort of communication link exists between the master and slave processors. As all the slave processors are controlled by the master processor.
Another important fact about the processors of an asymmetric multiprocessor is that they do not have any shared memory and operate independently of one another. For instance, if one of the processors is performing the OS tasks, the other one does the input-output tasks simultaneously. The asymmetric multiprocessors are used in applications requiring an embedded system to execute certain tasks simultaneously without requiring much power.
What is Symmetric Multiprocessing?
Symmetric multiprocessors are defined as the type of processors that are identical to each other and have the ability to perform shared tasks due to the presence of shared memory. This shared memory among the processors results in efficient task completion as the tasks can be divided among the processors and can be accomplished at a faster rate.
Unlike asymmetric multiprocessors, symmetric multiprocessors being identical in architecture, do not have a master-slave relationship. The task of the operating system is shared by all the processors equally. Tasks present in the common queue list are taken up and performed by all the processors one after another, ensuring that each of the processes performs different tasks.
Symmetric processors exchange certain kinds of communications among each other via shared memory. The symmetric multiprocessors have an added advantage over the asymmetric multiprocessors such as appropriate load balance, fault tolerance, and minimized CPU bottlenecks.
However, all processors being synchronized with each other makes the system design quite complex. In situations where one of the symmetric processors collapses, the computing capacity of the multiprocessing system is reduced.
Difference Between Symmetric and Asymmetric Multiprocessing
The following table highlights the key differences between a symmetric and asymmetric multiprocessor as follows –
| Parameter | Symmetric Multiprocessing | Asymmetric Multiprocessing |
| Processor types | All the processors are identical to each other. | All processors are not identical to each other. |
| Tasks of the operating system | The tasks of the operating system can be done by any symmetric CPU. | The tasks of the operating system are performed only by the master processor. |
| Communication | Due to the presence of shared memory, symmetric multiprocessors communicate with each other in order to execute the assigned tasks. | No sort of communication exists between the master and the slave processors as the slave processors are all managed by the master processor. |
| Task assignment | The tasks are assigned to the symmetric processors via a prepared queue list. | The slave processors are assigned tasks by the master processor. |
| Architecture | The system design of a symmetric multiprocessor is very complex due to the need for CPU synchronization. | The system design of an asymmetric multiprocessor is very simple and straightforward. |
| Expense | The symmetric multiprocessing systems are expensive as they have a complicated architectural design. | The asymmetric multiprocessing systems are comparatively cheaper as they have a simpler architectural design. |
| System complexity | The symmetric multiprocessors are having a complicated system design. | The asymmetric multiprocessors are having a simple system design. |
| System failure | When any of the symmetric processors fails, the other processor takes up the task of that failed CPU. | When the master processor collapses, the slave processor takes over as the master processor and performs its tasks. But when a slave processor fails, the other processor takes up its tasks. |
Conclusion
In conclusion, both symmetric and asymmetric multiprocessing systems improve system performance due to the presence of multiple CPUs that possess the ability to perform several tasks simultaneously. However, the most significant difference between them is that asymmetric multiprocessors follow the master-slave relationship due to which all the processors or CPUs of the asymmetric multiprocessing system are not alike.
On the other hand, symmetric multiprocessors are all identical in architecture as they share a common memory. However, owing to the complexity of symmetric multiprocessors, they are comparatively costlier than asymmetric multiprocessors with relatively simpler system architecture.
