Hardware Concepts
Hardware Concepts
All distributed systems consist of multiple CPUs; there are several different ways for organizing hardware. All distributed systems are categorized as MIMD (Multiple Instructions on Multiple Data).
MIMD computers can be divided into two groups:
- Multiprocessors: those systems that have shared memory.
- Multicomputers: those who do not have shared memory.
Both of the above groups can further be categorized as bus or switched.
Bus-Based Multiprocessors
Bus-based multiprocessors consist of several CPUs with high speed cache memory and memory connected to a common bus.
Switched Multiprocessors
(a) Figure shows the crossbar switch connects the CPUs and different memory modules. At every interaction is a tiny electronic cross point switch that can be opened and closed in hardware.
(b) Figure shows omega network, the network contains 2×2 switches each having two inputs and two outputs are connecting CPUs and memories.
Bus-Based Multicomputers
Above figure shows the bus-based multicomputer (i.e. no shared memory). Each CPU has its own local memory.
Switched Multicomputers
(a) Figure shows a Grid, these are best for problems that have an inherent two-dimensional nature.
(b) Figure shows a hypercube, which is an n-dimensional cube. Here the hypercube shown is four-dimensional. Here each CPU has n connections to other CPUs, thus complexity of wiring increases logarithmically with size.
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