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Memory

Memory. Memory. When we receive some instruction or information we retain them in our memory. Similarly a computer stores the instructions for solving a problem , the data to be processed , the intermediate results and the final results until they are displayed.

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Memory

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  1. Memory

  2. Memory • When we receive some instruction or information we retain them in our memory. Similarly a computer stores the instructions for solving a problem , the data to be processed , the intermediate results and the final results until they are displayed. • This storage unit s known as computer memory or store. • It consists of chips either on the motherboard or on a small circuit board attached to the motherboard. • This electronic memory allows the CPU to store and retrieve data quickly.

  3. Memory • Two types of built-in-memory: • Permanent memory. Some memory chips retain the data they hold, even when the computer is turned off. This type of permanent memory is called nonvolatile. • Non-Permanent memory. Other chips – in fact, most of the memory in a microcomputer-lose their contents when the computers power is shut down. This type of nonpermanent memory is called volatile.

  4. Nonvolatile Memory • Nonvolatile chips hold data even when the computer is unplugged. • During normal use, the data in these chips is only read and used- not changed- so the memory is called read only memory (ROM). • Specifically, chips that cannot be changed are called programmable read only memory (PROM). • PROM chips are often found on hard drives and printers. • They contain the instructions that power the devices. These instructions, once set, never need to be changed.

  5. Nonvolatile Memory • When a computer is turned on, it must know how to start. • ROM contains a set of start-up instructions called the basic input output system (BIOS) for a computer. FLASH MEMORY • Flash memory is a special type of nonvolatile memory. • It is often used in portable digital devices for storage. • Digital cameras, portable MP3 players, USB “keychain” storage devices all use flash memory.

  6. Volatile Memory • Volatile memory requires to store data. • The volatile memory in a computer is called random access memory (RAM). • RAM’s job is to hold programs and data while they are in use. • Physically, RAM consists of chips on a small circuit board. • Single inline memory modules (SIMMs) and dual inline memory module (DIMM) chips are found in desktop computers. • While the smaller, small outline DIMM (SO-DIMM) chips are found in laptop computers.

  7. RAMRandom Access Memory • It is also called main memory or direct access memory or read/write memory. • A program must be loaded into RAM before execution. • Data and instructions can be read and modified. • It play an important role in processing of computer.

  8. Types of RAM SRAM (Static Random Access Memory) • Retains contents as long as power is maintained. • Faster than DRAM. • SRAM is more expensive. • CPU does not wait to access data. • It is usually used to build a very fast memory known as cache.

  9. Types of RAM DRAM (Dynamic RAM) • Must be constantly refreshed. • Requires an electric current to maintain its electrical state. • The electrical charge of DRAM will decrease with time that may result in lose of data. • Used for most PC memory because of size and cost.

  10. Read Only Memory (ROM) • Programs and data that are permanently recorded at the factory. • The instructions can only be read and cannot be deleted. • Cannot be changed by the user. • When the computer is switched on ,the instructions in the ROM are automatically loaded into the memory of the computer.

  11. Types of ROMPROM • Programmable ROM • This form of ROM is initially blank. • The user can write data and programs on it. • The user can write data and instructions on it only once.

  12. EPROM • Stands for Erasable Programmable Read Only Memory • It is initially blank • The user can write data and programs on it. • The data and program written on it can be erased using ultraviolet rays.

  13. EEPROM • Stands for Electronically Erasable Programmable Read Only Memory • It is initially blank • The user can write data and programs on it. • The content of EEPROM can be modified easily. • The data and program written on it can be erased using electrical pulses.

  14. Cache Memory • Small block of very fast temporary memory • Speed up data transfer • It is located inside or close to CPU chip. • It is faster than RAM • Instructions and data used most frequently or most recently.

  15. Cache Step 3 Transfer to main CPU and cache P R O C E S S O R R A M Cache • Step 2 • Go to address in main memory and read Step 1 Processor requests data or instructions • Next processor request • Look first at cache • Go to memory

  16. Types of Cache • Internal cache • Level 1 (L1) • Built into microprocessor • Up to 128KB or 256 KB • External cache • Level 2 (L2) • Separate chips • 256KB or 512 KB • SRAM technology • Cheaper and slower than L1 • Faster and more expensive than memory

  17. KB – kilobyte 1024 bytes Some diskettes Cache memory MB – megabyte Million bytes RAM GB – gigabyte Billion bytes Hard disks CDs and DVDs TB – terabytes Trillion bytes Large hard disks Measuring Storage Capacity

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