Question

Computer Architecture - Cache Problems

4, Suppose memory addresses are n bits long and the cache can hold M bytes of data. If the cache block-size is 2 bytes and the cache is k-way set associative, what is the total size of the cache with a write-through policy? How would your answer change, if at all when the cache had a write-back policy?

Answer 1

Levels of the Memory Hierarchy Upper Level Access Time Staging Xfer Unit faster CPU Registers Registe Instr. Operands prog/compller 1-8 bytes K Bytes Cache S.01-001/bit cache cntl 8-128 bytes Blocks Main Memory Memory 100ns-1us $.01-001 Pages OS 512-4K bytes G Bytes Disk 10-10 čents Files Mbytes Larger Tape Lower Level 10

The Principle of Locality Probability of reference Address Space ° The Principle of Locality: pny nsmant ot tima.relatively small portion of the adress space at . Example: 90% of time in 10% of the code ° Two Different Types of Locality: . Temporal Locality (Locality in Time): If an item is referenced, it will tend to be referenced again soon. Spatial Locality (Locality in Space): If an item is referenced, items whose addresses are close by tend to be referenced soon. cache.7

Memory Hierarchy: Principles of Operation ° At any given time, data is copied between only 2 adjacent levels: Upper Level (Cache): the one closer to the processor - Smaller, faster, and uses more expensive technology er Level (Memory): t Bigger, slower, and uses less expensive technology Block . The minimum unit of information that can either be present or not present in the two level hierarchy Lower Level (Memory) To Procssor Upper Level (Cache) Blk X From Processor Blk Y cache.B