Explain memory hierarchy pdf

Studying such hierarchical structure in more detail is the topic of this chapter. Introduces the idea of a memory hierarchy in computer systems, how temporal and spatial locality allow them to achieve their goal. In the computer system design, memory hierarchy is an enhancement to organize the memory such that it can minimize the access time. Most of the computers were inbuilt with extra storage to run more powerfully beyond the main memory capacity. Host computer emulates guest operating system and machine. General purpose computers normally have a level 2 l2 cache on the same chip as the processor and l1 caches. The designing of the memory hierarchy is divided into two types such as primary internal memory and secondary external memory. Memory hierarchy is the hierarchy of memory and storage devices found in a computer. In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. An example of a structure with 4 levels is shown in figure 5. Designing for high performance requires considering the restrictions of. Virtual memory concepts are very similar to the concepts explained for cache.

The memory hierarchy system consists of all storage devices contained in a computer system from the slow auxiliary memory to fast main memory and to smaller cache memory. In practice, a memory system is a hierarchy of storage devices with different capacities, costs, and access times. The memory hierarchy was developed based on a program behavior known as locality of references. A hierarchy is an organizational structure in which items are ranked according to levels of importance. Sram is an acronym for static random access memory. Lecture 8 memory hierarchy philadelphia university. The idea centers on a fundamental property of computer programs known as locality. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controlling technologies. Memory references are generated by the cpu for either instruction or data access. Lower level upper level memory memory to processor from processor block x block y. While this is an effective model as far as it goes, it does not re. The memory hierarchy design in a computer system mainly includes different storage devices. Each level in the memory hierarchy contains a subset of the information that is stored in the level right below it. Frequently used information is found in the lower levels in order to minimize the effective access time of the memory hierarchy.

Programs with good locality tend to access the same set of data items over and over again, or they tend to access sets of nearby data items. Memory hierarchy affects performance in computer architectural design, algorithm predictions, and lower level programming constructs involving locality of reference. The following memory hierarchy diagram is a hierarchical pyramid for computer memory. Often visualized as a triangle, the bottom of the triangle represents larger, cheaper and slower storage devices, while the top of the triangle represents smaller, more expensive and faster storage devices. At any given time, data is copied between only two adjacent levels. The memory system is a hierarchy of storage devices with different capacities, costs, and access times.