Linking HW Components

1
Linking HW Components

• Davis Rajkumar (6th), Chp. 4

2
Overview

• Linking hardware
• Architectures
• Hardware and software interfaces

3
Linking Hardware

• In Chapter 4, linking refers to physical
  connection of hardware components
• Physical connection uses
• Bus for data paths
• Word size for width of data paths
• Machine cycle to process data from paths

4
Bus

• Internal components (those inside system unit)
  physically connected by
• Ribbon bus flat cable consisting of thin wires
  that connect device to motherboard
• Integrated circuit bus data and control paths
  incorporated into the motherboard that connect
  components on the motherboard
• Bus combination of power, data, and control
  lines
• Data lines carry bits
• Control lines carry system data addresses,
  commands, or system state data
• Power lines carry energy to power devices

5
Types of Buses

• Industry Standard Architecture (ISA)
• Micro Channel Architecture (MCA) IBMs bus
  alternative to ISA
• Video Electronic Standard Association (VESA)
  primarily video cards
• Extended ISA (EISA) upgraded ISA to 32 bits
• VESA Local Bus (VL) short lived upgrade to VESA
• Peripheral Component Interconnect (PCI)
• Accelerated Graphics Port (AGP) uses PCI

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Industry Standard Architecture (ISA)

• XT (8088) standard
• 8-bit (8 data lines)
• 20 address lines
• 1 MB max memory
• IRQs 2-7
• 4.77 MHz

• AT (80286) standard
• 16-bit
• 24 address lines
• 16 MB memory
• IRQs 2-15
• 8.33 MHz, 5MBps

• Used jumpers or switches to change settings
• Generally obsolete computer buses
• Some motherboards will have a slot for legacy
  devices

7
Obsolescence

• Obsolete--no longer used
• Technologies no longer used in computers may be
  found embedded in other products
• Consumer products from cars to watches use
  obsolete processors with small word size,
  limited instruction sets, and low clock speeds
• Legacy device
• Old devices from previous systems
• Still used because of unique function or software

8
Peripheral Component Interconnect

• PCI
• 32/64 bit bus, 33/66 MHz, 133 MBps/533 MBps,
  parallel data bus
• PCI-X
• 64 bit, 66/133 MHz, 533 MBps/4264 MBps
• Backward compatible with PCI
• PCI Express
• Two-way, serial connection (2 pair
  point-to-point)
• 2.5 GHz per lane (approx. 512 MBps)
• 32 lanes, 2.5 GHz, 16 GBps duplex
• Automatic configuration
• No jumpers or switches
• Necessary for plug-n-play

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Expansion Card Slots
10
Bus Comparison
Source http//www.intel.com/technology/pciexpress
/devnet/PCI-E_and_Networking.pdf
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Word Size

• Number of data bits processed or transferred at
  one time
• Historic word sizes 4, 8, 16, 32, 64 bits
• Current common word size
• Pentium 4 32-bit
• Itanium 64-bit
• SPARC selectable 32 or 64 bit
• Some 128-bit processors exist, but not common

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Machine Cycles

• Following fetch-execute cycle illustrates how
  components work together
• System-clock synchronizes activity
• Control Unit fetch gets data from memory (usually
  cache)
• Control Unit execute decodes opcode and initiates
  action of other components
• HexMac demo

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Architectures

• Architecture usually describes motherboards
  layout and supported technologies
• Single-bus process, memory, and peripherals all
  share same bus
• Multiple-bus
• More than one bus
• Example control paths separate from data bus

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Interfaces

• Boundary between two systems
• Interface frequently changes data from one format
  to another
• Keyboard scan impulse to scan code
• Word document format to printer format
• At hardware level, each bus and port has
  pin-out for exchanging data and control
• Serial port vs parallel port
• Serial bits sent one by one in stream
• Parallel bits sent along at once on multiple
  wires

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Controllers

• Special purpose processors
• Controls devices activity
• Converts data to format needed by bus or port

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External Buses

• Bus outside of system unit
• Universal Serial Bus (USB)
• Small Computer System Interface (SCSI)
• Used by peripherals

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Channels and Control Units

• Special purpose communications path
• Frequently used in conjunction with controller
  and external bus

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HW/SW Interface

• Means of communicating between hardware and
  programs
• File primatives
• Move
• Read
• Write
• Openestablish control block
• Access methods

19
Device Drivers

• Software that provides interface between devices
  and operating system
• Converts operating systems calls to instructions
  or impulses used by device

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Summary

• Linking connecting hardware
• Buses provide physical link
• Interfaces provide processing and software link