Dynamic Arbitration Algorithms
- A dynamic priority algorithm gives the system the capability for changing the priority of the devices while the system is in operation.
- The time slice algorithm allocates a fixed-length time slice of bus time that is offered sequentially to each processor, in the round-robin fashion.
- So, The service location independent.
- No preference is given to any particular device since each is allotted the same amount of time. To communicate with the bus.
- In a bus system that uses polling, the bus grant signal replaced by a set of lines called poll lines which connected to all units.
- These lines used by the bus controller to define an address for each device connected to the bus.
- Moreover, The bus controller sequences through the addresses in a prescribed manner.
- When a processor that requires access recognizes its address, it activates the bus busy line and then accesses the bus.
- Also, After a number of the bus cycle, the polling process continues by choosing a different processor.
- The polling sequence is normally programmable, and as a result, the selection priority can alter under program control.
- The least recently used (LRU) algorithm gives the highest priority to the requesting device that has not used the bus for the longest interval.
- Moreover, The priorities adjusted after a number of bus cycles according to the LRU algorithm.
- Also, With this procedure, no processor favored over any other since the priorities dynamically changed to give every device an opportunity to access the bus.
- In the first-come-first-serve scheme, requests served in the order received.
- Moreover, To implement this algorithm the bus controller establishes a queue arranged according to the time. That the bus requests arrive.
- Each processor must wait for its turn to use the bus on a first-in-first-out (FIFO) basis.
- The rotating daisy-chain procedure is a dynamic extension of the daisy chain algorithm.
- Also, Highest priority to the unit that is nearest to the unit that has most recently accessed the bus. (it becomes the bus controller).