computer hardware part1-1

8/12/2019 Computer Hardware Part1-1

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DATA REPRESENTATION (continue)

CODING SCHEMES

1. ASCII (American S tandard Code for Information Interchange )~ Normally used in PC and Midrange Server

2. EBCDIC (Extended Binary Coded Decimal Interchange Code )~ Mainframe, Supercomputer

3. Unicode~

To support language characters other than English & EuropeanWestern languages.~ More to expand in future use (6000 codes reserved for private and

30000 for general reserve)

NUMBER SYSTEMS

1. Decimal (Human nature)2. Binary (Machine/Computer nature)3. Hexadecimal (Computer nature ~ more compact form)


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Fig 3-12 Computer Circuit Data Representation by Bit ( Binary Dig it)


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Fig 3-14 Sample of ASCII and EBCDIC coding scheme


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Fig 3-15 How a letter is converted to Binary form and back


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Fig 3-16 The Number System


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RANDOM ACCESS MEMORY(Also called Primary Storage or Main Memory)

RAM (Random Access Memory )Memory Chips that stores data that can be read from or written to by the processor &other devices.

Random-access memory (RAM) is a form of computer data storage. Today, it takes theform of integrated circuits that allow stored data to be accessed in any order (that is, atrandom). "Random" refers to the idea that any piece of data can be returned in a constanttime, regardless of its physical location and whether it is related to the previous piece of

data.[1]

The word "RAM" is often associated with volatile types of memory (such as DRAM memorymodules), where the information is lost after the power is switched off. Many other types ofmemory are RAM as well, including most types of ROM and a type of flash memory calledNOR-Flash .


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DRAM


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SRAM


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RANDOM ACCESS MEMORY(Also called Primary Storage or Main Memory)

RAM (Random Access Memory )Memory Chips that stores data that can be read from or written to by the processor &other devices.

Types of RAM

Dynamic RAM (DRAM) the chips must be re-energized constantly or they will lose their content Variation of DRAM

Synchronous DRAM ( SDRAM ) synchronous to the system clock Double Data Rate RAM ( DDR SDRAM ) transfer data twice the rate of

SDRAM for each tick. DDR2 RAM double the rate of DDR RAM. Rambus DRAM (RDRAM ) use in Pipelining Processor.

Static RAM (SRAM) The chip not needed re-energized, but it is more expansive, but more reliable

Magnetoresistive RAM (MRAM) Stores data using magnetic charge instead of electrical charge. Possess greater capacity, consume less power, more reliable as data loss prevented.

MEMORY MODULE A small circuit board which RAM chips usually reside

TYPES OF MEMORY MODULE SIMM (S ingle Inline Memory Module) holds SDRAM & Connecting pins form a single set

of contact DIMM (Dual Inline Memory Module) holds SDRAM & Connecting pins form a two sets of

contact RIMM (Rambus Inline Memory Module) hold RDRAM


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Dynamic random-access memory (DRAM) is a type of random-access memory that stores each bit of data in a separatecapacitor within an integrated circuit. The capacitor can be eithercharged or discharged; these two states are taken to representthe two values of a bit, conventionally called 0 and 1 . Since even"nonconducting" transistors always leak a small amount, thecapacitors will slowly discharge, and the information eventuallyfades unless the capacitor charge is refreshed periodically .Because of this refresh requirement, it is a dynamic memory asopposed to SRAM and other static memory .

The main memory (the "RAM") in personal computers is dynamicRAM (DRAM). It is the RAM in desktops, laptops and workstationcomputers as well as some of the RAM of video game consoles.

The advantage of DRAM is its structural simplicity : only onetransistor and a capacitor are required per bit , compared to fouror six transistors in SRAM. This allows DRAM to reach very highdensities. Unlike flash memory, DRAM is volatile memory (vs.non-volatile memory), since it loses its data quickly when poweris removed. The transistors and capacitors used are extremely

small; billions can fit on a single memory chip.


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Fig 3-18 Dynamic RAM


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Stands for " Static Random Access Memory .SRAM is a type of RAM that stores data using a static method, in whichthe data remains constant as long as electric power is supplied to thememory chip . This is different than DRAM (dynamic RAM), which stores

data dynamically and constantly needs to refresh the data stored in thememory. Because SRAM stores data statically, it is faster and requiresless power than DRAM.

However, SRAM is more expensive to manufacture than DRAM becauseit is built using a more complex structure . This complexity also limits the

amount of data a single chip can store, meaning SRAM chips cannot holdas much data as DRAM chips . For this reason, DRAM is most often usedas the main memory for personal computers. However, SRAM iscommonly used in smaller applications, such as CPU cache memory andhard drive buffers. It is also used in other consumer electronics, fromlarge appliances to small children's toys.


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What is MRAM?

MRAM,- magnetoresistive RAM or magnetic RAM, is a type of nonvolatile RAM memory which uses magnetic charges in order to storedata . This is different from SRAM and DRAM, which use electriccharges to store data . The advantage of MRAM is that it retains datawhen power is turned off . It requires only a small amount of electricityto be able to store data bits. MRAMs work by using two iron plateswhich "sandwich" a thin insulating layer. One of the iron plates is amagnet which is set to a specific charge, whereas the other plate isvariable and allows for the polarity to change according to the pull ofthe external fields. Millions of magnetic "sandwiches" work together tomake up the MRAM memory device. MRAM requires less power thanother memory storage systems because it writes and stores data by

using magnetic fields instead of electrical circuits.


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CACHE CACHE : A type of RAM that stores frequently used data & instructions to

speed up the processing time a component that improves performance by transparently storing data such

that future requests for that data can be served faster. The data that isstored within a cache might be values that have been computed earlier orduplicates of original values that are stored elsewhere. If requested data iscontained in the cache (cache hit), this request can be served by simplyreading the cache, which is comparably faster

Two types of Cache

1. MEMORY CACHE - use to retrieve data & instruction from thememory

The L1 Cache directly built into processor chip withcapacity of 8kB to 128kB.

The L2 Cache slightly slower than L1, but larger capacity,

i.e. between 64kB to 64MB.The L3 Cache built separately from the processor onmotherboard. Only fitted to computers withadvanced L2 transfer cache.

2. DISK CACHE similar function, but retrieving from Hard Disk


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Fig 3-21 Memory Cache


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Fig 3-21 Memory Cache


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Fig 3-22 Disk Cache


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READ-ONLY MEMORY (ROM)

ROM is the permanently written data, instruction & information created bythe manufacturer, i.e. Startup instruction & System initial information during

boot.

Types of ROM

1. Programmable ROM (PROM) a blank ROM chip which aprogrammer can write instruction or program permanently

2. Electrical Erasable PROM (EEPROM ) a PROM that allows aprogrammer to erase the microcode with an electrical signal.

3. Flash Memory a variation of EEPROM that is used for specificpurpose, i.e. configuration of information on new hardware installed,or change daylight saving time.

CMOS (Complementary Metal-Oxide Semiconductor) a high speed chiptechnology used in some RAM, Flash Memory or any other type of memorychips that consumes little power (i.e. battery power to retain informationwhen the power to computer is off)


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ROM


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PROCESSOR INSTALLATION & UPGRADE

WHY UPGRADE?

To increase computer performance (mainly on the processingspeed) To allow compatibility for further upgrading

WHAT TO CONSIDER? Compatibility of components with the original motherboard

specifications.

WHAT ARE THE METHODS?1. Chip-for-chip : require to remove the existing processor chip2. & replace with new one into the socket on motherboard.3. Piggy-back : stack the new processor chip to the old one.4. Daughter-upgrade : new processor chip is physically on5. adapter card that plugs into motherboard.

TERM :1. PGA : P in-Grid Array2. ZIF : Z ero -Insertion F orce

BUSES


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BUSES

BUSES A set of parallel electrical channel that transports electrical signals in order tocommunicate among components on the motherboard.

Two parts of Buses

1. Data Bus transfer the actual data in electrical impulses.2. Address Bus transfer information about where the data should reside in

memory.

Size of Bus

Bus Width CPU Capacity

i.e. Larger bus width will make CPU transfer more data (fasterprocessor), having larger memory (bigger memory capacity) & supportmore instruction in terms of varieties & amount.

Type of Buses

1. System Bus part of the motherboard processor Communicates the processor & the memory

2. Expansion Bus Communicates either between processor to peripherals via ports &

connectors; or between processor to Expansion Boards via chipset;or Expansion Boards to Peripherals via ports & connectors.


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BUSES (continue..)

TYPES OF EXPANSION BUS

1. ISA Bus (Industry Standard Architecture) : - slower device, i.e.

modem, mouse.

2. PCI Bus (Peripheral Component Interconnect) :- high speed device,i.e. hard disk, network, video cards.

3. AGP Bus (Accelerated Graphic Port) :- i.e. interface of video card &memory.

4. USB (Universal Serial Bus) :- for hardware outside system unitwithout the requirement to install cards to Expansion Slots or toinstall hardware driver, i.e. Thumb Drive.

5. IEEE 1394 Bus/FireWire Bus :- i.e. for a very high speed video

equipment.

6. PC Card Bus :- i.e. interconnected to Slots inside a computer case,i.e. for solid state memory, network adapter modem. Example, thePCMCIA Cards (PC Memory Card International Association), inlaptop computers.


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Fig 3-23 The Buses


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EXPANSION SLOTS, ADAPTER CARDS & PERIPHERALS

EXPANSION SLOTS A socket on motherboard that can hold adapter cards.

ADAPTER CARDS/EXPANSION CARDSA circuit board that enhances functions of a component of thesystem unit or/and provides connections to peripherals.(e.g. sound, video, modem, network cards)

On Adapter Cards PC Cards ~ a thin, credit card-size device that adds memory,

storage, sound and any other capability to mobile computer. PCMCIA ~ a standard to ensure interchangeability of PC Cards

among mobile users all over around the world. Flash Memory Card ~ removable flash memory device to transfer

data/information to & from mobile & desktop computers .PERIPHERALS

A device that connects to the system unit and is controlled bythe processor of the computer.Example :- External Modem, Joystick & Wheel, AdditionalNumeric-pad & etc.

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