Relazione d'Inglese "Memory overview"

Relazione d'Inglese

"Memory overview"

The terms Main Memory refers to the space of the memory where data the instructions are stored in phase of execute or elaboration.

Memory can be split into two main categories: volatile and nonvolatile. Volatile memory loses any data as soon as the system is turned off; it requires constant power to remain viable. Nonvolatile memory does not lose its data when the system or device is turned off. A number of types of memory fall into this category. The most familiar is ROM, but Flash Memory storage devices such as CompactFlash or SmartMedia cards are also forms of nonvolatile memory.

- R.A.M. = Random Access Memory, is a memory chip an integrated circuit made of millions of transistor and capacitors. The opposite of RAM is "Serial Access Memory" (S.A.M.). SAM stores data as a series of memory cells that can only be accessed sequentially (like a cassette tape).

There are some types of RAM currently available: SRAM, DRAM, SDRAM and VRAM.

The S.R.A.M. (Static RAM) is used primarily for cache. SRAM uses multiple transistors, typically four to six, for each memory cell.

The D.R.A.M. ( Dynamic RAM) is the most common type of memory in use today. Inside a dynamic RAM chip, each memory cell holds one bit of information and is made up of two parts: a transistor and a capacitor. These are, of course, extremely small transistors and capacitors so that millions of them can fit on a single memory chip. The capacitor holds the bit of information.

The S.D.R.A.M. (Synchronous RAM) is a new DRAM technology that uses a clock to synchronize signal output on a memory chip.

The V.R.A.M. (Video RAM) is faster than DRAM, and it is used by graphics cards.

- R.O.M = Read-Only Memory, is an integrated circuit programmed with specific data when it is manufactured. ROM chips are used not only in computers, but in most other electronic items as well.

There are four basic ROM types:

P.R.O.M. (Programmable Read-Only Memory), can only be programmed once. They are more fragile than ROMs. A jolt  of static electricity can easily cause fuses in the PROM to burn out.

E.P.R.O.M. (Erasable Programmable Read-Only Memory), can be rewritten many times. In an EPROM, the cell at each intersection has two transistor, in comparison at other memory.

E.E.P.R.O.M. (Electrically Erasable Programmable Read-Only Memory), remove the biggest drawbacks of EPROM. In EEPROM the chip does not have to removed to be completely erased to change a specific portion of it.

Flash Memory, is considered a solid state storage device. It is used for easy and fast information storage in such devices as digital cameras and home video game consoles.

In the computer to be a Virtual Memory, who is a common part of most operating system on desktop computers. With virtual memory, what the computer can do is look at RAM for areas that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application.