Multiprocessors
Definition:
A Multiprocessor
is an interconnection of two or more CPUs between memory and IO devices. The term ‘processor’ in
multiprocessor can mean either a CPU or an input-output processor(IOP).
However, a system with a single CPU and one or more IOPs is usually not
included in the definition of a multiprocessor system unless the IOP has
computational facilities comparable to a CPU. As it is most commonly defined, a
multiprocessor system implies the existence of multiple CPUs, although usually
there will be one or more IOPs as well.
Bus-based
multiprocessors
Flynn’s Classification of multiple-processor machines:
{SI, MI} x {SD, MD} = {SISD,
SIMD, MISD, MIMD}
SISD = Single
Instruction Single Data
Classical Von Neumann machines.
SIMD = Single
Instruction Multiple Data
Also called Array Processors or
Data Parallel machines.
MISD Does not
exist.
MIMD Multiple
Instruction Multiple Data
Control parallelism.
A Taxonomy of Parallel Computers
NUMA
Non Uniform Memory Access
COMA
Cache Only Memory Access
MPP
Massively Parallel Processor
COW
Cluster Of Workstations
CC-NUMA Cache
Coherent NUMA
NC-NUMA
No Cache NUMA
Characteristics
of Multiprocessors
Multiprocessors
System = MIMD
An
interconnection of two or more CPUs with memory and I/O equipment
» a single CPU and one or more
IOPs is usually not included in a multiprocessor system
Unless the IOP has computational facilities comparable to a CPU
Computation
can proceed in parallel in one of two ways
1) Multiple
independent jobs can be made to operate in parallel
2) A single job
can be partitioned into multiple parallel tasks
Classified by
the memory Organization
1) Shared memory
or
Tightly-coupled
system
» Local memory + Shared memory
higher degree of interaction between tasks
2) Distribute
memory or Loosely-coupled system
» Local memory + message
passing scheme (packet or message )
most efficient when
the interaction between tasks is minimal
