Chap06 Memory
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Transcript of Chap06 Memory
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Chapter 6
Managing Memory
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You Will Learn
About the different kinds of physical memory
and how they work
How to upgrade and troub
leshoot memory How DOS and Windows 9x view and manage
memory
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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
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ROM on the Motherboard
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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)
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DRAM Storage
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SRAM Storage
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SRAM and DRAM
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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
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How SRAM Is Used in Different
Memory Caches
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How Memory Caching Works
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Different Types of SRAM
Synchronous SRAM
Burst SRAM
Pipelined burst SRAM
Asynchronous SRAM
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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
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Summary ofDRAM Technologies
continued
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Summary ofDRAM Technologies
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SIMM Technologies
Rated by speed, measured in nanoseconds (ns)
Can use either EDO or FPM technology
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DIMM Technologies
Rated by speed and amount of memory theyhold
Use either BEDO or synchronous SDRAM
(SDRAM) Variations of SDRAM
Regular SDRAM
DDR SDRAM (SDRAM II) SyncLink (SLDRAM)
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DIMM Technologies
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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
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RIMM Technologies
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Parity and Error Checking
Parity
Error-checking procedure in which every byte haseither 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
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Parity
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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
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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
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Example of an RDRAM Memory
Configuration
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Installing Memory
Protect chips against static electricity
Use a ground bracelet
Turn off power and remove cover to case
Handle memory modules with care
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Installing a SIMM Module
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Installing a DIMM Module
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Installing a DIMM Module
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Troubleshooting Memory
What if the computer does not recognize newSIMMs, DIMMs, or RIMMs, or if memoryerror messages occur?
What if the system locks up or you regularlyreceive error messages about illegal operations,and General Protection Faults occur duringnormal operation and you have not just
upgraded memory?
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How DOS Addresses Physical Memory
Assigning addresses to both RAM and ROM:
Occurs during booting (sometimes called memorymapping)
Is done by every OS
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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)
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Areas of the Memory Map
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Memory Map of Upper Memory
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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
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UsingHimem.sys
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Using Emm386.exe
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Creating and Using Upper Memory
Blocks
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Chapter Summary
How DOS and Windows 9x manage memory
Memory
Required for a system to work
Stored on microchips, which are often stored onmemory modules (SIMMs, DIMMs, or RIMMs)
Adding more memory can sometimes greatly
improve performance