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Chapter 6. Managing Memory. You Will Learn…. About the different kinds of physical memory and how they work How to upgrade and troubleshoot memory How DOS and Windows 9x view and manage memory. Physical Memory Review. Temporarily holds data and instructions as CPU processes them

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chapter 6

Chapter 6

Managing Memory

you will learn
You Will Learn…
  • About the different kinds of physical memory and how they work
  • How to upgrade and troubleshoot memory
  • How DOS and Windows 9x view and manage memory
physical memory review
Physical Memory Review
  • Temporarily holds data and instructions as CPU processes them
  • Two categories
    • ROM
      • Retains its data when PC is turned off
      • Stores data on chips socketed or soldered to circuit boards
    • RAM
      • Loses its data when PC is turned off
      • Housed on SIMMs, DIMMs, or RIMMs
rom on the motherboard
ROM on the Motherboard
  • Consists of memory chips that contain programs (ROM BIOS) that are acid-etched into the chips and cannot be changed
  • EPROM (erasable programmable ROM) and EEPROM (electrically erasable programmable ROM) chips can be reprogrammed
ram on the motherboard
RAM on the Motherboard
  • Serves as main memory
  • Provides a memory cache
  • Two categories
    • Dynamic RAM (DRAM)
      • Needs to be refreshed by the memory controller
      • Usually stored on DIMMs, less commonly on RIMMs
    • Static RAM (SRAM)
static ram technologies
Static RAM Technologies
  • Provide faster access than DRAM because data does not need to be constantly rewritten to SRAM
    • SRAM chips are made of transistors that can hold a charge
    • DRAM chips are made of capacitors that must be recharged
  • Due to expense of SRAM chips, most computers have a little SRAM and a lot of DRAM
different types of sram
Different Types of SRAM
  • Synchronous SRAM
  • Burst SRAM
  • Pipelined burst SRAM
  • Asynchronous SRAM
dynamic ram technologies
Dynamic RAM Technologies
  • Always stored in SIMMs, DIMMs, or RIMM modules
  • Major differences among modules:
    • Width of the data path that each accommodates
    • The way data moves from system bus to module
  • Goal is to increase overall throughput while retaining accuracy
simm technologies
SIMM Technologies
  • Rated by speed, measured in nanoseconds (ns)
  • Can use either EDO or FPM technology
dimm technologies
DIMM Technologies
  • Rated by speed and amount of memory they hold
  • Use either BEDO or synchronous SDRAM (SDRAM)
  • Variations of SDRAM
    • Regular SDRAM
    • SyncLink (SLDRAM)
rimm technologies
RIMM Technologies
  • Use a narrower data path than SIMMs or DIMMs in order to provide faster data transmission
  • Data moves from the system bus sequentially through each RIMM module
parity and error checking
Parity and Error Checking
  • Parity
    • Error-checking procedure in which every byte has either an even or an odd number of ones
    • Every byte occupies nine rather than eight bits
  • ECC (Error-Correcting Code)
    • New method of error checking that not only detects but also corrects an error in a single bit
upgrading memory
Upgrading Memory
  • Use type, size, density, and speed of memory that motherboard supports
  • Match memory modules already installed
  • Guidelines for selecting high-quality chips
    • Tin or gold leads
    • Remanufactured and used modules
    • Re-marked chips
how much and what kind of memory to buy
How Much and What Kind of Memory to Buy
  • How much memory do I have/need?
  • How many memory slots on motherboard? What type/size of memory do they support?
  • How much additional memory is cost-effective?
  • Match memory modules to the motherboard
installing memory
Installing Memory
  • Protect chips against static electricity
  • Use a ground bracelet
  • Turn off power and remove cover to case
  • Handle memory modules with care
troubleshooting memory
Troubleshooting Memory
  • What if the computer does not recognize new SIMMs, DIMMs, or RIMMs, or if memory error messages occur?
  • What if the system locks up or you regularly receive error messages about illegal operations, and General Protection Faults occur during normal operation and you have not just upgraded memory?
how dos addresses physical memory
How DOS Addresses Physical Memory
  • Assigning addresses to both RAM and ROM:
    • Occurs during booting (sometimes called memory mapping)
    • Is done by every OS
areas of the memory map
Areas of the Memory Map
  • Logical divisions determined by memory addresses rather than physical location
    • Conventional (base): First 640K
    • Upper: 640K up to 1024K
    • Extended: Above 1024K
      • First 64K are called high memory area (HMA)
dos utilities that manage memory
DOS Utilities That Manage Memory
  • Himem.sys
    • Device driver for all memory above 640K
    • Allows DOS to access memory addresses above1 MB
  • Emm386.exe
    • Contains software that loads device drivers and other programs into upper memory
chapter summary
Chapter Summary
  • How DOS and Windows 9x manage memory
  • Memory
    • Required for a system to work
    • Stored on microchips, which are often stored on memory modules (SIMMs, DIMMs, or RIMMs)
  • Adding more memory can sometimes greatly improve performance