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For each of the following statements, state if they are true or false. (a) A cac

ID: 2079757 • Letter: F

Question

For each of the following statements, state if they are true or false. (a) A cache using a write-back policy writes back to the main memory simultaneously as it writes to the cache. (b) Two important properties of a virtual memory are to give the illusion of a very large memory and to give memory protection between two concurrently running programs. (c) A unit called the memory management unit (MMU) is a common solution to perform fast translations from virtual page numbers to physical page numbers. (d) Modern high-performance processors do not use multi-level caches because they are too expensive and give little performance benefits.

Explanation / Answer

a.)True

The advantage of write-back caches is that not all write operations need to access main memory, as with write-through caches.

— If a single address is frequently written to, then it doesn’t pay to keep writing that data through to main memory.

— If several bytes within the same cache block are modified, they will only force one memory write operation at write-back time.

b.)True

Provide at least two modes, indicating whether the running process is a user process or an operating system process.

c.)True.

d.)True.

Modern processors use high-performance cache replacement policies that outperform traditional alternatives like least recently used (LRU). Unfortunately, current cache models do not capture these high-performance policies as most use stack distances, which are inherently tied to LRU or its variants. Accurate predictions of cache performance enable many optimizations in multicore systems.