An arbiter controls access to a common resource. It uses a rotating-priority sch
ID: 1715655 • Letter: A
Question
An arbiter controls access to a common resource. It uses a rotating-priority scheme in responding to requests on lines R1 through R4. Initially, R1 has the highest priority and R4 the lowest priority. After a request on one of the lines receives service, that line drops to the lowest priority, and the next line in sequence becomes the highest-priority line. For example, after R2 has been serviced, the priority order, starting with the highest, becomes R3, R4, R1, R2. What will be the sequence of grants for the following sequence of requests: R3, R1, R4, R2? Assume that the last three requests arrive while the rst one is being serviced.
Explanation / Answer
WHEN R3 REQUEST CAME .... R3 BEING SERVICED (HIGHEST)
R1
R4
R2 (LOWEST)
WHEN R1 REQUEST CAME R1 BEING SERVICED (HIGHEST)
R4
R2
R3 (LOWEST)
WHEN R4 REQUEST CAME R4 BEING SERVICED (HIGHEST)
R2
R3
R1 (LOWEST)
WHEN R2 REQUEST CAME R2 BEING SERVICED (HIGHEST)
R3
R1
R4 (LOWEST)
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