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Crossbar Networks
Figure 2.3:
An
crossbar network (a) straight switch setting; and (b) diagonal switch setting.
|
- While the single bus can provide only a single connection, the crossbar can provide simultaneous connections among all its inputs and all its outputs.
- The crossbar contains a switching element (SE, also called a cross-point) at the intersection of any two lines extended horizontally or vertically inside the switch (see Fig. 2.3).
- Simultaneous connections between
and
are made.
- The number of SEs (switching points) required is 64 and the message delay to traverse from the input to the output is constant, regardless of which input/output are communicating.
- In general for an
crossbar, the network complexity, measured in terms of the number of switching points, is
while the time complexity, measured in terms of the input to output delay, is
.
- Notice also that the crossbar is a nonblocking network that allows a multiple input/output connection pattern (permutation) to be achieved simultaneously. However, for a large multiprocessor system the complexity of the crossbar can become a dominant financial factor.
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Cem Ozdogan
2006-12-27