Difference between SIMD and MIMD

SIMD and MIMD are the two main computer architectures. These architectures are utilized to enhance the performance of specific computing activities. The quantity of data and instruction streams serves as the foundation for this classification. SIMD is a computer architecture that allows a single instruction to be executed on numerous data streams. In contrast, the MIMD computer architectures may run multiple instructions on different data streams. The main objective of this classification is to categorize parallel processing. It operates by considering the processor's internal architecture, which begins with the connectivity structure among processors or the flow of data via the systems.

In this article, you will learn about the difference between SIMD and MIMD. But before discussing the differences, you must know about SIMD and MIMD, with their advantages and disadvantages.

What is SIMD?

SIMD is an abbreviation for "Single Instruction Multiple Data". It is a type of parallel computer architecture that Michael Flynn classifies under Flynn's categorization. In this SIMD architecture, a single instruction is implemented to multiple data streams. It is made up of a single control signal that calls many discrete processing units. As a result, all of the processing units accept the identical instruction from the control unit and apply it to different data components.

It employs a shared memory unit that is separated into several modules. Therefore, the memory unit may communicate with all the processing units at the same time. It consumes less memory because it utilizes a single copy of instruction on several data streams. Furthermore, SIMD architecture needs a single instruction decoder that helps to minimize the overall system cost.

Advantages and Disadvantages of SIMD

There are various advantages and disadvantages of SIMD. Some main advantages and disadvantages of SIMD are as follows:

Advantages

1. It utilizes less memory because only one copy of the instruction is kept in system memory.
2. As the SIMD architecture has a single instruction stream and absolute synchronization, creating, interpreting, and debugging programs is done in a very simple way.
3. Over the Control Unit (CU), it may overlap control flow instructions and numerous scalar operations to overlap.
4. It utilizes implicit synchronization to deliver excellent inter-process communication.
5. SIMD total cost is reduced because it uses only one instruction decoder.

Disadvantages

1. It contains huge register files, which enhance power utilization and chip area.
2. As it only has one core, the system's speed is limited.

What is MIMD?

MIMD is an abbreviation for "Multiple Instruction Multiple Data Stream". It contains computer systems with numerous processor units, data streams, and instruction streams. It utilizes numerous instructions for various data sets at the same time. MIMD systems are the most complex configuration, but they also ensure efficiency. It offers high concurrency by allowing numerous processors to run concurrently in the same time frame in addition to the same operation of processors. It works effectively with both distributed and shared memory models.

This architecture doesn't require any extra control unit that helps to decrease the system's overall cost. It also ensures that conditional statements, such as if/else expressions, that are executed efficiently. It is due to the processing unit's independence. It is more flexible and well-suited to tasks that need more complicated and diversified calculations, such as general-purpose computing and AI apps.

Advantages and Disadvantages of MIMD

There are various advantages and disadvantages of MIMD. Some main advantages and disadvantages of MIMD are as follows:

Advantages

1. MIMD's asynchronous characteristic may accelerate the execution pace of instructions that take an unlimited time.
2. It offers a high level of versatility by utilizing several control threads.
3. It doesn't need an extra Control Unit and hence has no extra expense.
4. It allows efficient execution of conditional statements (i.e., if-then-else) as the CPU is autonomous and may take any random decision path.
5. These processors are found in the most modern desktop, laptop, and mobile processors.

Disadvantages

1. It is appropriate for apps that need a wide range of CPU and data heavy-tasks (such as game renders and video editing).

Key differences between SIMD and MIMD

There are various key differences between SIMD and MIMD. Some of the key differences between SIMD and MIMD are as follows:

1. SIMD architecture is based on synchronous processing, in which the processing element works on a single program. On the other hand, MIMD architecture includes an asynchronous mechanism for operating processor elements across many communication programs.
2. SIMD is commonly utilized for issues that require a large number of computations, with multiple processors doing the same function simultaneously. On the other hand, MIMD is widely utilized for issues that divide algorithms into discrete and independent pieces, each part of which is allocated to a distinct processor for a concurrent solution.
3. Each processing element in MIMD architecture keeps its own copy of the program, which increases memory needs. On the other hand, SIMD architecture takes less memory because it only saves one copy of the program.
4. SIMD architecture is less complicated and more efficient. On the other hand, MIMD architecture is more complicated and efficient.
5. SIMD is inexpensive because hardware such as decoders is in less demand. On the other hand, MIMD is expensive because it requires one decoder for each processing element..
6. SIMD only has one decoder. On the other hand, MIMD architecture has multiple decoders.
7. SIMD refers to latent or implicit synchronization. On the other hand, MIMD architecture is accurate or explicit synchronization.

Head-to-head comparison between SIMD and MIMD

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

Conclusion

In conclusion, SIMD and MIMD are two major computer architectures. SIMD architecture supports synchronous processing, in which a single instruction is executed on several data streams simultaneously. In contrast, MIMD architecture utilizes an asynchronous approach in which multiple instructions work on numerous data streams. When compared to the MIMD architecture, the SIMD architecture is less complex and efficient. Implementing Control Unit overlap significantly impacts SIMD and MIMD architecture performance, depending on its uniformity. SIMD architecture outperforms MIMD in uniform CU (Control Unit) overlap cases. In contrast, MIMD architecture outperforms SIMD in cases of non-uniform CU overlap.