Question

Which of the following cache mapping can prevent bus thrashing?

(a) fully associative

(b) direct mapping

(c) n way set associative

(d) 2 way associative

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This question is from Size of Cache in chapter Memory Systems of Embedded Systems

Answer 1

The correct choice is (c) n way set associative

To explain: Only one data can be accessed in direct mapping that is, if one word is accessed at a time, all other words are discarded at the same time. This is known as bus thrashing which can be solved by splitting up the caches so there are 2,4,..n possible entries available. The major advantage of the set associative cache is its capability to prevent the bus thrashing at the expense of hardware.