For this question, see the state machine on the final page of this test:

$($a$)$Fill out the following chart for a two$-$processor system executing the following

sequence of instructions and adhering to the cache protocol in the diagram. Assume

the following:

The data from addresses $110$ and $120$ are initially stored in both processors'

caches and marked as clean$/$shared$.$

The cache block size is $1$ word.

"Before" and "After" refer to the block's state in cache before the instruction is

executed and after it is executed, respectively.

$($b$)$ The MESI protocol is similar to the protocol in the diagram, except that it has an

additional state called "Exclusive." If a block is marked "Exclusive," that means that

it is present in only one processor's cache and not shared in any other processor's

cache, and that it is clean $($has not been written$).$ What is the advantage of this

additional state?

Fill the table below for the MESI protocol $($using assumptions from part $($a$)$ above$)$: