previous bytes. Different memory devices are arranged according to the capacity, speed and cost as shown in Figure . . Main Memory Hard Disk Smaller capacity, faster access time and higher cost larger capacity,slower access time and Lower cost Cache Memory Figure .
Memory Hierarchy . . Random-Access Memory (RAM) The main memory is otherwise called as Random Access Memory . This is available in computers in the form of Integrated Circuits (ICs).
It is the place in a computer where the Operating System, Application Programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. The smallest unit of information that can be stored in the memory is called as a bit. The memory can be accessed by a collection of bits which is called as a byte. RAM is a volatile memory, which means that the information stored in it is not permanent.
As soon as the power is turned off, whatever data that resides in RAM is lost. It allows both read and write operations. . .
Types of RAM There are two basic types of RAM • Dynamic RAM (DRAM) • Static RAM (SRAM) These two types differ in the up the memory retrieval process. Due to its higher cost, the CPU comes with a smaller size of cache memory compared with the size of the main memory. Without cache memory, every time the CPU requests the data, it has to be fetched from the main memory which will consume more time. The idea of introducing a cache is that, this extremely fast memory would store data that is frequently accessed and if possible, the data that is closer to it.
This helps to achieve the fast response time, Where response Time, (Access Time) refers to how quickly the memory can respond to a read / write request. Figure . shows the arrangement of cache memory between the CPU and the main memory. CPU Cache Main Memory Fast Slow Figure .
Cache Memory Arrangement . Secondary Storage Devices A computer generally has limited amount of main memory which