Memory

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Memory

  1. 1. Title of the presentation Anjali G anjalig2009@gmail.com dwww.facebook.com/Anjali Geetha twitter.com/Anjali Geetha in.linkedin.com/in/Anjali G 9497879952
  2. 2. DIFFERENT TYPES OF MEMORIES IN A COMPUTER INCLUDING REGISTERS
  3. 3. INTRODUCTION  Computer memory is any physical device capable of storing information temporarily or permanently. two types: volatile and non volatile
  4. 4. REPRESENTATION OF MEMORY
  5. 5. VOLATILE MEMORY Volatile memory is a temporary memory that loses its contents when the computer or hardware device loses power. Computer RAM is a good example of a volatile memory  Most modern volatile memory is either Static RAM or dynamic RAM. SRAM:-  SRAM uses six transistors per bit. SRAM is faster and more reliable than the more common DRAM . While DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds. Unfortunately SRAM is much more expensive to produce than DRAM. Due to its high cost, SRAM is often used only as a memory cache. SRAM is generally used for high-speed registers & caches.
  6. 6. A typical SRAM cell is made up of six MOSFET. Each bit in an SRAM is stored on four transistors(M1, M2, M3, M4) that form two cross-coupled inverters. Main Needs: • to provide a direct interface with the CPU at speeds not attainable by DRAMs • to replace DRAMs in systems that require very low power consumption. DRAM:- DRAM is a type of random-access memory that stores each bit of data in a separate capacitor within an IC. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit. Dynamic RAM needs regular refresh cycles to prevent its contents being lost. The advantage of DRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to four or six transistors in SRAM.
  7. 7. DRAM is usually arranged in a rectangular array of charge storage cells consisting of one capacitor and transistor per data bit.
  8. 8. VIRTUAL MEMORY When computer lacks RAM; needed to run a program or operation Virtual memory is used. Virtual memory combines your computer’s RAM with temporary space on your hard disk. The purpose of virtual memory is to enlarge the address space, the set of addresses a program can utilize. The operating system divides virtual memory into pages, each of which contains a fixed number of addresses. Each page is stored on a disk until it is needed. When RAM runs low, virtual memory moves data from RAM to a space called a paging file. Moving data to and from the paging file frees up RAM to complete its work. OS is translating virtual addresses into real addresses. The process of translating virtual addresses into real addresses is called mapping. The copying of virtual pages from disk to main memory is known as paging.
  9. 9. NONVOLATILE MEMORY Non-volatile memory is computer memory that can retain the stored information even when not powered.  Examples of non-volatile memory include read-only memory , flash memory, most types of magnetic computer storage devices (e.g. hard disks, floppy discs and magnetic tape) Read-only memory (ROM) is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware. Flash memory is an electronic non-volatile computer storage device that can be electrically erased and reprogrammed. Flash memory was developed from EEPROM. There are two main types of flash memory, which are named after the NAND and NOR logic gates.
  10. 10. REGISTERS A special, high-speed storage area within the CPU.  All data must be represented in a register before it can be processed. The number of registers that a CPU has and the size of each help determine the power and speed of a CPU. Only assembly language programs can manipulate registers. Register performs: 1. Fetch: The Fetch Operation is used for taking the instructions those are given by the user and the Instructions those are stored into the Main Memory will be fetch by using Registers. 2. Decode: The Decode Operation is used for interpreting the Instructions means the Instructions are decoded means the CPU will find out which Operation is to be performed on the Instructions. 3. Execute: The Execute Operation is performed by the CPU. And Results those are produced by the CPU are then Stored into the Memory and after that they are displayed on the user Screen.
  11. 11. TYPES OF REGISTERS Memory Address Register: -This register holds the memory addresses of data and instructions. This register is used to access data and instructions from memory during the execution phase of an instruction. Program Counter:- The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 microprocessors. It keeps track of the the next memory address of the instruction that is to be executed once the execution of the current instruction is completed. Accumulator Register:- Register is used for storing the Results those are produced by the System. Memory Data Register :- MDR is the register of a computer's control unit that contains the data to be stored in the computer storage(e.g. RAM), or the data after a fetch from the computer storage Index Register:-A hardware element which holds a number that can be added to the address portion of a computer instruction to form an effective address. Data Register:-A register used in microcomputers to temporarily store data being transmitted to or from a peripheral device.
  12. 12. THANK YOU
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