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Memory Organization - Computer Fundamental

ram, rom, dram, sram, vram, fram, prom, eprom, eeprom
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Estimated read time: 12 min

Memory Organization


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Memory System

A memory system is a very simple system exhibits a wide range of technology and types.

Random Access Memory (RAM)

RAM is the place in a computer where the operating system, application programs, and data in current usage are kept so that they can be quickly accessed by the processor. RAM reads and writes faster than the other kinds of storage in a computer like the hard disk, floppy disk, and co-rom. However, the data in RAM is stored temporarily till the computer is running. When the power of the computer cut then RAM loses its data. When you switch on your computer, the operating system and other files are once again loaded into RAM, usually from your hard disk.

RAM is known as ‘random access memory’ because any storage location can be accessed randomly. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to specific locations. In addition to disk, floppy disk, and CD-ROM (Compact Disk – Read Only Memory) storage, another important from of storage is read-only memory (ROM), a more expensive kind of memory that retains data when the computer is turned off. Every computer comes with a small amount of ROM that holds just enough programming so that the operating system can be loaded into RAM each time the computer is turned on.

The Size of RAM

RAM is small, both in physical size (it is stored in microchip modules) and for the data that it can hold. It is much smaller than your hard disk. A typical computer may come with 32 million bytes of RAM and a hard disk that can hold 4 billion bytes. RAM comes in the form of ‘discrete’ (meaning separate) microchip modules that are plugged in the holed in the computer’s motherboard. These holes connect through a bus or set of electrical paths to the processor. The hard disk, on the other hand, stores data on a magnetized surface that looks like a phonograph record.

Today, personal computers are available with 16 or more megabytes of RAM, usually increasing in multiples of 8 megabytes. Most personal computers are designed to allow you to add additional RAM modules up to a certain limit (for example, up to 64, 128, or 256 megabytes). Having more RAM in your computer reduces the number of times that the computer processor has to read data in from your hard disk, an operation that takes much longer than reading data from RAM. (RAM access time is expressed in nanoseconds; hard disk access time is expressed in milliseconds.).

Kinds of RAM

RAM is of only two kinds, i.e. Dynamic and static. Which stores every kind of data and makes it quickly accessible to a microprocessor? However, there is some special RAM that can be both dynamic and static like video RAM. Which stores data intended for the display screen, enabling images to girt display faster.

  1. Flash RAM
  2. Video RAM
  3. Static RAM (SRAM)
  4. Dynamic RAM (DRAM)

Dynamic RAM (DRAM)

Dynamic RAM uses a kind of capacitor that needs frequent power refreshing to retain its charge. Because reading a DRAM discharges its contents, a power refresh is required after each read. RDAM must be refreshed about every 15 microseconds. DRAM is the least expensive kind of RAM. Synchronous DRAM (SDRAM) is a generic name for various kinds of DRAM that are synchronized with the clock speed that the microprocessor is optimized. Synchronization tends to increase the number of instructions that the processor can perform in a given time. The speed of SDRAM is rated in MHz rather than in nanoseconds (ns). This makes it easier to compare the bus speed and the RAM chip speed. You can convert the RAM clock speed to nanoseconds (ns) by dividing the chip speed into 1 billion ns (which is equal to one second.) For Ex-, an 83 MHz RAM would be equivalent to 12 ns.

Static RAM (SRAM)

Static RAM is more expensive, requires four times the amount of space for a given amount of data than dynamic RAM. Unlike, dynamic RAM, it does not need to be power-refreshed and is therefore faster to access. One source gives a typical access time as 25 nanoseconds in contrast to an access time of 60 nanoseconds for dynamic RAM.

Video RAM

Video RAM as the name signifies is a general form of RAM used to store image data for the video display monitor. All types of video TAM are special arrangements of dynamic RAM (DRAM). Video RAM is really a buffer between the processor and the display monitor and it’s often known as the frame buffer. When images are to be sent to the display, they are first read by the processor and then written to video TAM. From video TAM (the frame buffer), the data ties converted by a RAM digital-to-analog converted (RAMDAC) into analog signals that are sent to the display presentation mechanism such as a cathode ray tube (CRT). Usually, video RAM comes in a 1 or 2 megabyte package and is located on the video or graphics card in the computer.

Flash RAM

Flash RAM sometimes called flash memory is a type of constantly powered non-volatile memory that can be erased and reprogrammed in units of memory called blocks. It is a variation of electrically erasable programmable read-only memory (EEPEOM), which unlike flash memory, is erased and rewritten at the byte level. Flash memory, is erased and rewritten at the byte level. Flash memory is often used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed or rewritten, the flash memory can be written in block (rather than byte) sizes, making it easy to update. On the other hand flash memory is not useful as random access memory (RAM) because RAM needs to  be addressable at the byte (not the block) level.

Flash memory derives its name because the microchip is organized in a way so that a section of memory cells are erased in a single action or ‘flash’. Flash memory is used in digital cellular phones, digital cameras, LAN switches, PC cards for notebook computer, digital set-up boxes, embedded controllers, and other devices.

Read Only Memory (ROM)

Read only memory is most commonly used to store system –level programs that need to be available to the PC at all times? The most common example is the system BIOS program, which is stored in a ROM and is used to boot up the system. When you first turn on the PC the system memory is empty, so there has to be something for the PC to use when it starts up. These programs are stored at the manufacturing time and could not be changed later on.

                    DRAM                     SRAM           Video RAM     Flash RAM            

Kinds of ROM

The contents of a ROM cannot be changed, there are times when being able to change the contents of a ROM becomes very useful. There are several ROM variants that can be changed under certain circumstances: these can be thought of as mostly read only. The following are the different types of ROM with a description of their relative modifiable:

  1. Read Only Memory (ROM)
  2. Programmable ROM (PROM)
  3. Erasable Programmable ROM (EPROM)
  4. Electrically Erasable Programmable ROM (EEPROM)

Read Only Memory (ROM)

A regular ROM is constructed from hard-wired logic, encoded in the silicon itself, similar to a processor. It is designed to perform a specific function and cannot be changed. This is inflexible and so regular ROM are only used generally for programs that are static (not changing often) and mass-produced.

Programmable ROM (PROM)

A type of ROM that can be programmed using special equipment; it can be written to, but only once. It is useful for companies that make their own ROM for the software they write. This is because when they change their code they can create new proms without requiring expensive equipment. This is similar to the way s CO-ROM reorder works by letting you create or write programs onto bland one and then letting you read from them many times, in fact, programming a PROM is also called burning a CD-R, and it is comparable in terms of its flexibility.

Erasable Programmable ROM (EPROM)

An EPROM is a ROM that can be erased and reprogrammed. A little glass window is installed at the top of the ROM package, through which you can actually see the chip that holds the memory. Ultraviolet light of a specific frequency can be shined through this window for a specified period of time, which will erase the EPROM and allow it to be reprogrammed again. Obviously, RPROM is much more useful than a regular PROM, but it does require the erasing light. This technology is analogous to a reusable CD-RW (Compact Disk – Read Write).

Electrically Erasable Programmable ROM (EEPROM)

The next level of erase ability is the EEPROM, which can be erased under software control. This it’s the most flexible type of ROM, and it’s now commonly used for holding BIOS programs. The term flashes BIOS or doing BIOS upgrade by flashing refers to reprogramming the BIOS EEPROM with a special software program.

Question from memory organization chapter:

  1. What is memory organization?
  2. What is memory system?
  3. What is RAM?
  4. What is full form of RAM?
  5. What is random access memory?
  6. What is the size of ram?
  7. Types of ram
  8. How many types of RAM?
  9. How many types of random access memory?
  10. What dynamic ram
  11. What is full form of DRAM?
  12. What is dynamic random access memory?
  13. What is SDRAM?
  14. What is synchronous DRAM?
  15. What is synchronous dynamic random access memory?
  16. What is full form of SDRAM?
  17. What static ram
  18. What is full form of SRAM?
  19. What is static random access memory?
  20. What is video RAM?
  21. What is flash RAM?
  22. What is ROM?
  23. What is read only memory?
  24. Types of ROM
  25. How many types of ROM?
  26. How many types of read only memory?
  27. What is PROM?
  28. What is full form of PROM?
  29. What is programmable ROM?
  30. What is full form of programmable ROM?
  31. What is programmable read only memory?
  32. What is EPROM?
  33. What is full form of EPROM?
  34. What is erasable programmable ROM?
  35. What is full form of erasable programmable ROM?
  36. What is erasable programmable read only memory?
  37. What is EEPROM?
  38. What is full form of EEPROM?
  39. What is electrically erasable programmable ROM?
  40. What is full form of electrically erasable programmable ROM?
  41. What is electrically erasable programmable read only memory?

2 comments

  1. second ago
    prom
  2. second ago
    prom
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