Parallel Processing and Super-Scalar Operation 399
The major disadvantage of ring topology is its relative slowness in communicating between distant
nodes, especially when they are wide apart. In this case, the communication time might be reduced by
breaking down a ring to multiple smaller rings, as illustrated in Figure 13.8 (b). Note that, in this case,
the rectangle denotes the interconnection between two rings (two different data paths or busses). The
same hierarchy may be maintained in the case of multiple rings.
13.3.7 Single Bus
Single bus is the most natural way to interconnect multiple nodes, as shown in Figure 13.9 . In this case, the
nodes represent processors or memory modules of a multiprocessor and they are interconnected through
a single bidirectional bus, allowing data communication between any two nodes at any given time. For
this purpose, an ef cient bus-arbitrator is necessary. This is one of the main disadvantages of single-bus
topology, that concurrent multiple communication links may not be established in such a con guration.
However, the bandwidth may be increased by increasing the number of signal lines within the bus itself.
Figure 13.8 Ring networks (a) Single (b) Multiple
(a) (b)
Figure 13.9 Single bus networks
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