Question: After sending address and appropriate command on the bus, why does it have to wait for the command to be accepted?
I thought that requesting for bus and getting the bus grant had already guaranteed that the cache controller has the exclusive access to the bus.
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kayvonf
Correct, but "wait for command to be accepted" on this slide meant wait for all other processors to acknowledge that they have seen the message.
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shabnam
An important realization here was that steps 3-7 constitute the "shoutout for data" in the snooping based coherence based studied before. Thus these 5 steps need to happen atomically.
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ruoyul
For a uniprocessor, aren't step 4 and 7 unnecessary? since the single processor is guaranteed to have exclusive access to the bus, right?
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drayson
There are other things connected to the bus that also need access (most obviously the memory, but potentially other non-processor devices as well depending on the system) -- a bus with only one device on it wouldn't be very useful!
Question: After sending address and appropriate command on the bus, why does it have to wait for the command to be accepted?
I thought that requesting for bus and getting the bus grant had already guaranteed that the cache controller has the exclusive access to the bus.
This comment was marked helpful 0 times.
Correct, but "wait for command to be accepted" on this slide meant wait for all other processors to acknowledge that they have seen the message.
This comment was marked helpful 0 times.
An important realization here was that steps 3-7 constitute the "shoutout for data" in the snooping based coherence based studied before. Thus these 5 steps need to happen atomically.
This comment was marked helpful 0 times.
For a uniprocessor, aren't step 4 and 7 unnecessary? since the single processor is guaranteed to have exclusive access to the bus, right?
This comment was marked helpful 0 times.
There are other things connected to the bus that also need access (most obviously the memory, but potentially other non-processor devices as well depending on the system) -- a bus with only one device on it wouldn't be very useful!
This comment was marked helpful 0 times.