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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

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Memory

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  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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

  6. 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 +

  7. 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 +

  8. 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?

  9. 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)

  10. 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

  11. 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

  12. Overview Of Hardware Components

  13. Windows 98 Operating System • DOS - Where we came from • How to get around • Formatting disks • Copying files • Some basic commands • File and directory structure

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