computer system memory

The system memory is the place where the computer holds current programs and data that are in use. The term “memory” is somewhat ambiguous; it can refer to many different parts of the PC because there are so many different kinds of memory that a PC uses. However, when used by itself, “memory” usually refers to the main system memory, which holds the instructions that the processor executes and the data that those instructions work with. Your system memory is an important part of the main processing subsystem of the PC, tied in with the processor, cache, motherboard and chipset.

Memory plays a significant role in the following important aspects of your computer system:

Performance: The amount and type of system memory you have is an important contributing factor to overall performance. In many ways, it is more important than the processor, because insufficient memory can cause a processor to work at 50% or even more below its performance potential. This is an important point that is often overlooked.
Software Support: Newer programs require more memory than old ones. More memory will give you access to programs that you cannot use with a lesser amount.
Reliability and Stability: Bad memory is a leading cause of mysterious system problems. Ensuring you have high-quality memory will result in a PC that runs smoothly and exhibits fewer problems. Also, even high-quality memory will not work well if you use the wrong kind.
Upgradability: There are many different types of memory available, and some are more universal than others. Making a wise choice can allow you to migrate your memory to a future system or continue to use it after you upgrade your motherboard.
This section describes various aspects of the system memory, including how the system memory works, the different technologies used, packaging styles and how operating systems and programs organize and use the memory in the PC. Special attention is given to error detection and correction (which is in my opinion a greatly under-emphasized subject today) as well as details on how to know what type of memory works in different kinds of PCs.

Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s

The term memory hierarchy is used in the theory of computation when discussing performance issues in computer architectural design, algorithm predictions, and the lower level programming constructs such as involving locality of reference. A ‘memory hierarchy’ in computer storage distinguishes each level in the ‘hierarchy’ by response time. Since response time, complexity, and capacity are related[1], the levels may also be distinguished by the controlling technology.

The many trade-offs in designing for high performance will include the structure of the memory hierarchy, i.e. the size and technology of each component. So the various components can be viewed as forming a hierarchy of memories (m1,m2,…,mn) in which each member mi is in a sense subordinate to the next highest member mi-1 of the hierarchy. To limit waiting by higher levels, a lower level will respond by filling a buffer and then signaling to activate the transfer.

There are four major storage levels.

Internal – Processor registers and cache.
Main – the system RAM and controller cards.
On-line mass storage – Secondary storage.
Off-line bulk storage – Tertiary and Off-line storage.


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