Multiprocessor

In multiprocessing, all CPUs may have equal functions or some may be reserved for specific functions.

Different ways of using a multiprocessor include:

• As a uniprocessor, such as single instruction, single data (SISD)
• Inside a single system for executing multiple, individual series of instructions in multiple perspectives, such as multiple instruction, multiple data (MIMD)
• A single series of instructions in various perspectives, such as single instruction, multiple data (SIMD), which is usually used for vector processing
• Multiple series of instructions in a single perspective, such as multiple instruction, single data (MISD), which is used for redundancy in failsafe systems and, occasionally, for describing hyper-threading or pipelined processors

Benefits of using a multiprocessor include:

• Enhanced performance
• Multiple applications
• Multiple users
• Multi-tasking inside an application
• High throughput and/or responsiveness
• Hardware sharing among CPUs

Communication architecture of a multiprocessor:

• Message Passing
• Independent address space for every processor
• Processor communication by means of message passing
• Processors include private memories
• Concentrates attention on high-priced, non-local operations


• Shared Memory
• Processor communication is done by means of a shared address space
• Processor communication is done by means of shared memory read/write
• Convenient on small-scale devices
• Lower latency
• Non-uniform memory access (NUMA) or symmetric multiprocessing (SMP)