Which of the following statements are true ?

A. In the write-through policy, only the cache is updated

B. In the write-back policy, both cache and main memory are updated

C. Cache coherence problems exist in multiprocessors with private caches because of the need to share writable data

D. Cache coherence problem can be solved by means of hardware-only scheme

Choose the correct answer from the options given below:

1. AA, B Only
2. BB, C Only
3. CC, D Only
4. DA, B, C Only η

Pick an option to check yourself, or open the answer below.

Show answer & explanation

Correct answer: C. C, D Only

Explanation

Write-through updates cache and memory together (A false); write-back updates only the cache until the block is replaced (B false). Private caches holding shared writable data cause coherence problems (C true), and hardware-only schemes such as snooping solve them (D true).