Time Shared Common bus Interconnection Structures
- A common bus multiprocessor system consists of a number of processors connected through a common path to a memory unit.
- A time shared a common bus for five processors shown in the figure.
- Also, Only one processor can communicate with the memory or another processor at any given time.
- Moreover, Transfer operations conducted by the processor that is in control of the bus at the time.
Figure: Time-shared common bus organization
- Any other processor wishing to initiate a transfer must first determine the availability status of the bus and only after the bus becomes available, the processor addresses the destination unit to initiate the transfer.
- Also, A command issued to inform the destination unit, what operation is to perform.
- The receiving unit recognizes its address in the bus and responds to the control signals from the sender, after which the transfer initiated.
A single common-bus system is restricted to one transfer at a time.
- Moreover, This means that when one processor is communicating with the memory, all other processors are either busy with internal operations or must be idle waiting for the bus.
- As a consequence, the total overall transfer rate within the system limited by the speed of the single path.
- A more economical implementation of a dual bus structure depicted in the figure.
- Here we have a number of local buses each connected to its own local memory and to one or more processors.
- Also, Each local bus may connect to a CPU, an IOP, or any combination of processors.
- A system bus controller links each local bus to a common system bus.
- The I/O devices connected to the local IOP, as well as the local memory, are available to the local processor.
- The memory connected to the common system bus shared by all processors.
- If an IOP connected directly to the system bus, the I/O devices attached to it may make available to all processors.
- Also, Only one processor can communicate shared the memory with the shared memory. And other common resources through the system bus at any given time.
- The other processors are kept busy communicating with their local memory and I/O devices.