Crossbar Switch Interconnection Structures
- Figure shows a crossbar switch interconnection between four CPUs and four memory modules.
- The small square in each cross point is a switch that determines the path from a processor to a memory module.
- Each switch point has to control logic to set up the transfer path between a processor and memory.
- It examines the address that placed on the bus to determine whether its particular module is being addressed.
- It also resolves multiple requests for access to the same memory module on a predetermined priority basis, the figure shows the functional design of a crossbar switch connected to one memory module.
- The circuit consists of multiplexers that select the data, address. And control from one CPU for communication with the memory module.
- Priority levels established by the arbitration logic to select one CPU when two or more CPUs attempt to access the same memory.
- The multiplex controlled with the binary code that generated by a priority encoder within the arbitration logic.
- A crossbar switch organization supports simultaneous transfers from memory modules because there a separate path associated with each module.
- However, the hardware required to implement the switch can become quite large and complex.