Unformatted text preview: computers. A crossbar switch configuration is shown in Figure 9.5. The blue switches indicate closed switches. A processor can be connected to only one memory at a time, so there will be at most one closed switch per column. The second type of switch is the 2 ± 2 switch . It is similar to a crossbar switch, except that it is capable of routing its inputs to different destinations, whereas the crossbar simply opens or closes the communications channel. A 2 ± 2 interchange switch has two inputs and two outputs. At any given moment, a 2 ± 2 switch can be in one of four states: through , cross , upper broadcast , and lower broadcast , as shown in Figure 9.6. In the through state, the upper input is CPU1 MM1 MM2 MM3 MM4 CPU4 CPU3 CPU2 Open switch Closed switch FIGURE 9.5 A Crossbar Network a) c) b) d) FIGURE 9.6 States of the 2 ± 2 Interchange Switch a. Through b. Cross c. Upper Broadcast d. Lower Broadcast...
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- Summer '14
- Crossbar switch, crossbar switches, b. Cross