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Memory. RAM is stored on internal microchips on-line ROM (Read only Memory) Stored permanently on chips in the computer Usually not altered or erased. Gives the computer its instructions when turned on

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memory
Memory
  • RAM is stored on internal microchips on-line
  • ROM (Read only Memory)
    • Stored permanently on chips in the computer
    • Usually not altered or erased.
    • Gives the computer its instructions when turned on
    • Contains the BIOS-Basic input/output System, amongst other things, which tells your computer how to operate and allows the software to take over.
computer memory
Computer Memory
  • Memory refers to data stored on microchips, storage refers to data stored permanently on disk, tap, CD - etc. A more definitive definition of Memory vs Storage
  • Early systems had 640K of RAM which was primarily reserved for DOS, this is sometimes termed base memory which is up to 1MB.
  • Current systems still reserve 640 K of RAM for DOS, as well as other functions such as keyboard buffer and video memory.
  • There are many different types of RAM that have evolved to serve various purposes. This link provides a RAM guide
computer memory3
Computer Memory
  • Primary Storage (System Memory)
    • RAM (Random Access Memory) - on line
      • Short Term - lost when computer is turned off
      • Limited in amount available
      • Very fast, random access to information
  • Dynamic Ram (DRAM)
    • Cheaper type of Memory chip - pretty slow
    • Access time to chip measured in nanoseconds
      • Chip name -12=120 nano. -7=70 nano.
    • If CPU runs faster than memory you have problems
      • Takes at least two clock cycles to refresh memory
      • Wait states for DRAM
cache memory caching
CacheMemory Caching
  • Caching techniques avoid wait states.
  • A block of high speed RAM, typically Static RAM (SRAM) placed between the CPU and ordinary RAM
  • Cache Controller keeps likely needed data in Cache memory for high speed access.
  • Larger the cache memory, the more likely that the needed data will be available
  • Typical cache today is 64K - 128 K but can be higher
  • Primary cache or (L1) is in the CPU chip (typically 16K) Secondary Cache memory is external up until the P6.
mass storage
Mass Storage
  • Secondary Storage (Mass Storage)
    • Permanent storage and retrieval ability
    • Very large capacity
    • Not as fast as on line memory
  • Hard, Floppy, Zip disks, tape, CD-ROM Cartridge
    • Sequential and Random Access Media
hard drives
Hard Drives
  • Speed influenced by:
    • How fast the drive spins (7200-10,000 rpm)
    • Average Access (Seek) Time (5-8 milliseconds)
    • Data Transfer Rate-measured in MB/Sec.

80+ Mb/Sec. Depending on the interface.

    • SCSI fastest and can be daisy chained
  • Storage Capacity
    • Used to be constrained to .5 GB by DOS 5/6 and BIOS
    • Interfaces such as ATA (.5 GB max), SCSI and IDE drives were not limited but had be partitioned.
    • Windows 95 allowed 2 GB, Windows 98 - no limit
    • More is better - typically 4 GB +
floppy drives
Floppy Drives
  • Floppy Drives (3.5" and 5.25" Disk Drives)
    • 3.5" Disk Drive (High density = 1.44MB Medium = 720K)
    • 5.25" Disk Drive (High Density = 1.2MB Double = 540K)
  • Formatting Floppy Disks
    • Format a: formats disk to capacity of drive
    • Format a: /f:720 formats medium density
    • incorrect format will mess up your disk
  • Write protect
  • Disk Care
  • Floptical Disks up to 230Mb, Zip Disks 100MB +
input output devices
Input / Output Devices
  • Input devices
    • Keyboards 84 keys old std. 101 is current
    • Mouse (Serial Port)
    • Light Pens
    • Touch Screen
    • Voice
    • Joy Stick
    • Scanners
    • Video/Camera
    • Modem?
output devices
Output Devices
  • Output Devices
  • Monitor (soft copy) CRT
    • MDA - Monochrome Display Adapter (2 colors)
    • CGA - Color Graphics Adapter -RGB- (16 colors)
    • EGA - Enhanced Graphics Adapter (64 colors)
    • VGA - Video Graphics Array (256 & up) & SVGA
  • Prior to VGA video signal was digital, almost all VGA is no analog
  • Pixels - Resolution (640X480 to 1280X1024)
output devices continued
Output Devices continued
  • Standard is SVGA - 800 X 600, 1024x768
    • Influences on speed are memory, horizontal (kHz) and vertical scan rate (Hz)Refresh rate (Hz), interlacing,
    • VESA tries to establish video standards
    • 3D Video AcceleratorsAGP
  • Printers
    • Impact Printers - dot matrix (9 and 24 pin); daisy wheel
    • InkJet - better image resolution but slow
    • Thermal - specialized application
    • Thermal transfer (wax) - best color printers
    • Laser - 300 -1200 dpi
communication ports
Communication Ports
  • Serial Ports - Com Port, RS-232C
    • One lane wide - turns 8, 16, 32 wide path into 1
    • Speed measured in BPS 600 - 115,200 potential to go as high as 1 mill. in near future.
    • Usually used for modems and some printers
  • Parallel Ports
    • 8 lanes wide - Lpt ports
    • Most commonly used for printers but with bi-directional other connections are possible
    • Up to 100 times faster than serial
windows 98 operating system
Windows 98 Operating System
  • DOS - Where we came from
    • How to get around
    • Formatting disks
    • Copying files
    • Some basic commands
    • File and directory structure