Here we observe a lag between the blue response and the green response. This is because the memory can take an arbitrary amount of time to respond to requests. We are hence not guaranteed continuous usage of the response bus. However the request bus is still being utilized and hence the bus as a whole is not idle.
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placebo
Also note that this continuous stream of incoming requests cannot continue forever. You need to limit the number of requests you can handle in light of the limited size of data structures like the request table (which helps map requests to responses). That means that if the max number of handleable requests has been reached, no other requests can be processed until some responses are received and those outstanding requests are taken care of.
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vvallabh
Question: Why are there 4 outstanding requests? Aren't orange and blue complete, so only green and red are outstanding?
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placebo
@ vvallabh, well initially there were four outstanding requests. But yeah, later on it does appear that a couple of them were taken care of, so only the green and red requests remain outstanding towards the right of the slide.
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rutwikparikh
To add on to @placebo, requests that appear after the maximum number of requests (request table is full) has been reached could be sent a NACK (Negative Acknowledgement) and we can retry these requests after a few cycles.
Here we observe a lag between the blue response and the green response. This is because the memory can take an arbitrary amount of time to respond to requests. We are hence not guaranteed continuous usage of the response bus. However the request bus is still being utilized and hence the bus as a whole is not idle.
This comment was marked helpful 1 times.
Also note that this continuous stream of incoming requests cannot continue forever. You need to limit the number of requests you can handle in light of the limited size of data structures like the request table (which helps map requests to responses). That means that if the max number of handleable requests has been reached, no other requests can be processed until some responses are received and those outstanding requests are taken care of.
This comment was marked helpful 0 times.
Question: Why are there 4 outstanding requests? Aren't orange and blue complete, so only green and red are outstanding?
This comment was marked helpful 0 times.
@ vvallabh, well initially there were four outstanding requests. But yeah, later on it does appear that a couple of them were taken care of, so only the green and red requests remain outstanding towards the right of the slide.
This comment was marked helpful 0 times.
To add on to @placebo, requests that appear after the maximum number of requests (request table is full) has been reached could be sent a NACK (Negative Acknowledgement) and we can retry these requests after a few cycles.
This comment was marked helpful 0 times.