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Computer memory

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Computer memory

  1. 1. Storage and Memory Nguyen Duc An Nguyen Huu Ngoc Chi
  2. 2. Did you know… • Storage : Provides capacity for all the files and information you need( e.g. capacity of the computer’s hard disk) • Memory : Provides your working space ( e.g. the amount of RAM installed in the computer)
  3. 3. OverviewPrimary- storage of intermediate data- necessary to run the computer- RAM, CacheSecondary- long-term storage of data- HDDTertiary - CD, DVD, memory card...Off-line- disconnected storage- unplugged USB flash drive- external HDD
  4. 4. Memory In computing memory refers to the physical devices used to store programs or data on the temporary or permanent basis for use in a computer or other digital electronic device Main memory is divided into two parts : - Random Access memory ( RAM ) should be better known as Read Write Memory - Read Only Memory (ROM)
  5. 5. Random Access Memory (RAM)• Structure : A set of memory chips, each of them is an integrated circuit (IC) made of millions of transistors and capacitors• Volatile - their state is lost or reset when power is removed from the system.• Usage : Holds data/application programs from input devices or storages• Capacity : Determines the number and size of the program can be run at the same time as well as the amount of data that can be processed immediately.• Bus : processing speed
  6. 6. Types of RAMStatic Random Access Memory Dynamic Random Access(SRAM) Memory (DRAM)• Semi conductor memory • Store each bit of memory in• Use flip-flop to store each bit of capacitor in an integrated circuit memory so does not need to be • Real capacitors leak charge so periodically refreshed capacitors need to be refreshed• Faster and consumes low power periodically• Expensive and have complex • Simple structure ( 1 transistor and structure (6 transistors) so not use 1 capacitor per bit) so it has very in high capacity applications high density
  7. 7. Read only memory (ROM)• Has contents which are fixed when the chip is manufactured• Holds the bootstrap loader part of the operating system• Retains its data when the computer is switched off
  8. 8. Types of ROMProgrammable ROM (PROM)-Empty of data when the chip ismanufactured, can beprogrammed by the user. Onceprogrammed the data cannot beerased.Erasable PROM (EPROM)-Like PROM only the chip can beremoved from the computer andthe program erased and anotherstored in its place usingultraviolet light.Electrically EPROM (EEPROM)-Like EPROM but electricity isused to erase and reprogram
  9. 9. Cache memory• Faster and expensive than RAM• It improves the computer’s performance• Processor can use it to store frequently accessed data and program instructions• It is two types : - L1 : primary cache (inside the processor) - L2 : secondary cache (in the motherboard or near the microprocessor)
  10. 10. Storage• Storage – any devices that are capable of holding information, even when the power is off (non-volatile).• Ex: Floppy disk drive, hard disk drive, USB flash disk,...• Offline storage – type of storage that can be removed and can be accessed from any computers when connected.
  11. 11. Types of storage device • Optical storage devices • Magnetic storage devices • Flash memory devices
  12. 12. Optical storage devicesCompact Disc (CD) DVD Blu-ray Disc Capacity: 700 MB Capacity: 4.7 GB Capacity: 25 GBAvailable from 1982 Available from 1995 Available from 2006
  13. 13. Optical storage devices Advantages:  Small and portable  Cheap to produce  Large market of music, movies and games  Most desktop computers or laptops are equipped with CD/DVD/Blu-ray drive Disadvantages: x Fragile, easy to get scratched x Slower data transferring rate x Required specified drives to write data to the discs x Limited number of writes
  14. 14. Magnetic storage devicesFloppy disk• First available in 1971• Capacity: 1.44 MB (3 1⁄2-inch floppy disk)• Discontinued.• Since 2010, no motherboard is still manufactured with the support of floppy disk drive.
  15. 15. Magnetic storage devicesHard disk drive (HDD)• First introduced in 1956 Became dominant in the 1960s Capacity keeps increasing Max. capacity: 4 TB (as of 2013)• Continuously improved.• Maintained an important position of modern servers and PCs.
  16. 16. Magnetic storage devices Advantages (HDD):  Large and increasing capacity  High transferring speed  No data loss when power is off (non-volatile)  Cheap price compared to other storage media (cost per MB) Disadvantages (HDD): x Possible damages and data loss due to ‘head’ crash x Because of working on mechanism basis, it will be eventually broken x In case of internal hard drive, it is not easy to be transferred to another computer x High power consumption
  17. 17. Flash memory devicesUSB Flash drive• Commercially available in 2000• Max. capacity: 1 TB (as of 2013)• Small size• Ideal solution for storing small data
  18. 18. Flash memory devicesSolid state drive (SSD)• First introduced in 1995• Max. capacity: 1 TB (as of 2013)• Very high transferring speed in comparison to normal physical hard disk
  19. 19. Flash memory devices Advantages:  Large and increasing capacity  High transferring speed  Small size, portability  Low power consumption  Work more quietly than physical hard drive Disadvantages: x High price compared to hard disks (cost per MB) x Limited number of reads/writes (write endurance rating) x Easy to lose because of small size
  20. 20. You didn’t hear that?Thank you

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