Flynn's Classification
Flynn's Classification
Flynn's Classification
Parallel computing is a computing where the jobs are broken into discrete
parts that can be executed concurrently. Each part is further broken down to a
series of instructions. Instructions from each part execute simultaneously on
different CPUs. Parallel systems deal with the simultaneous use of multiple
computer resources that can include a single computer with multiple
processors, a number of computers connected by a network to form a parallel
processing cluster or a combination of both.
Parallel systems are more difficult to program than computers with a single
processor because the architecture of parallel computers varies accordingly
and the processes of multiple CPUs must be coordinated and synchronized.
The crux of parallel processing are CPUs. Based on the number of instruction
and data streams that can be processed simultaneously, computing systems
are classified into four major categories:
Flynn’s classification –
1. Single-instruction, single-data (SISD) systems –
An SISD computing system is a uniprocessor machine which is capable of
executing a single instruction, operating on a single data stream. In SISD,
machine instructions are processed in a sequential manner and computers
adopting this model are popularly called sequential computers. Most
conventional computers have SISD architecture. All the instructions and data
to be processed have to be stored in primary memory.
Example Z = sin(x)+cos(x)+tan(x)
The system performs different operations on the same data set. Machines
built using the MISD model are not useful in most of the application, a few
machines are built, but none of them are available commercially.
4. Multiple-instruction, multiple-data (MIMD) systems –
An MIMD system is a multiprocessor machine which is capable of executing
multiple instructions on multiple data sets. Each PE in the MIMD model has
separate instruction and data streams; therefore machines built using this
model are capable to any kind of application. Unlike SIMD and MISD
machines, PEs in MIMD machines work asynchronously.