table of Contents
Outline
Memory classification
Main categories below:
Memory Hierarchy
The memory has three indexes: capacity, speed, price;
their relations can be represented by the following figure:
Figure from top to bottom, getting lower and lower price, more slowly, increasing the capacity;
Storage hierarchy is mainly reflected in the cache - the main memory, the main memory - the secondary storage, the following structure:
- Cache - mainly to solve the CPU and main memory main memory speed mismatch, because the cache speed is higher than the speed of main memory, as long as the CPU will require recent information transferred to the cache, CPU can get information directly from the cache to improve memory access speed; due to the small-capacity cache, main memory and therefore needs to constantly transferred to the cache contents, so that the contents of the cache to be replaced, the mobilization of data between main memory and cache done automatically by the hardware, transparent to the programmer;
- Main memory - secondary storage capacity mainly to solve the problem, auxiliary storage lower speed than the main memory, and CPU can not exchange data directly, but it is much larger capacity than the main memory, can store large amounts of information is not being used, when the CPU needs data , the information is transferred to the auxiliary storage by the CPU to access main storage; main memory and secondary storage data mobilization was done by common hardware and operating system;
- From the perspective of CPU, cache - close to the main memory cache speed, higher than the main memory; and a price close to the main memory capacity;