Computer Systems Computer Architecture and Organization

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Computer SystemsComputer Architecture and
Organization Fundamental Computer Hardware
Components
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Computer Architecture vs Organization

• Architecture is those attributes visible to the
  programmer
• Instruction set, number of bits used for data
  representation, I/O mechanisms, addressing
  techniques.
• e.g. Is there a multiply instruction?
• Organization is how features are implemented
• Control signals, interfaces, memory technology.
• e.g. Is there a hardware multiply unit or is it
  done by repeated addition?
• More examples?
• Architecture
• Organization

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Computer Architecture vs Organization

• All Intel x86 family share the same basic
  architecture
• The IBM System/370 family share the same basic
  architecture
• This gives code compatibility
• At least backwards
• Organization differs between different versions

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Hardware Components - Memory
Source http//www.scm.tees.ac.uk/users/a.clements
/MemIntro/memory.htm
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Hardware Components - Memory

• Volatility
• Non-volatile Memory information still retained
  after power off
• e.g., ROM (Read-Only Memory)
• Volatile Memory information not retained when
  power off
• e.g., RAM (Random-Access Memory)
• Error correction and detection
• Hamming code
• Parity

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Hardware Components - Memory

• SRAM
• value is stored on a pair of inverting gates
• very fast but takes up more space than DRAM (4 to
  6 transistors)
• DRAM
• value is stored as a charge on capacitor (must be
  refreshed)
• very small but slower than SRAM (factor of 5 to
  10)

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Hardware Components Main Memory

• Where the instructions and local data for a
  program reside while a program is executed
• Composed of bits which are grouped into into
  addressable units of bytes
• Bytes are in turn paired into words which can be
  treated as single storage/transfer units
• Implementation Technologies
• Magnetic (Core)
• Semiconductor

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Hardware Components Main Memory

• Core (1950s and 1960s)
• consists of loops of a magnetic material
• two magnetized directions represent 1 and 0
• non-volatile, expensive, bulky
• destructive read
• reading a core erased data stored in it
• necessary to restore the data as soon as it had
  been extracted
• Semiconductor (1970 -)
• integrated-circuit technology
• first semiconductor memory in 1970
• 256 bits on one chip, about the size of a core,
  faster, but cost is higher, nondestructive read
• milestone in 1974
• cost per bit of semiconductor lt cost per bit of
  core
• generations 1K, 4K, 16K, 64K, 256K, 1M, 4M, 16M
  bits, ... on a single chip

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Hardware Components - Disk

• Composed of one or more platters

Spindle
R/W Head (1 per surface)
Surface7
Platters
Tracks
Platter
Track0
Sectors
Track
Surface1
Actuator
Surface0
Cylinder
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Hardware Components - Disks

• Address of a block of data on a disk (Cylinder,
  Track, Sector)
• To access a block of data Seek, Rotate, Transfer
• seek position head over the proper track (3 to
  15 ms. avg.)
• rotational latency wait for desired sector
  0.5 RPM (avg.)
• transfer grab the data (one or more sectors)
  30 to 80 MB/sec
• Access time seek time rotational latency
  data transfer time
• Example A disk has an average seek time 12ms,
  rotational latency 5.6 ms, and transfer rate
  5MB/sec. What is the average time to read a
  block of 512 byte sector?
• Data block size and organization of data blocks
  on the disk matter!

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Hardware Components CPU

• ALU (Arithmetic and Logic Unit)
• The component which
• - actually performs arithmetic and logical
  operations
• - governs flow of a program
• Constructed by electronic circuits
• Control Unit, responsible for
• reading an instruction
• determining what operation
• determining addresses of operands
• then instructing ALU to perform operation
• Control process can be hardwired or using
  micro-programming (similar to RTL) to implement
  instruction set of a computer
• Registers, Cache, etc.

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CPU Example Pentium 4

• Processor executes simple microinstructions, 70
  bits wide (hardwired)
• 120 control lines for integer datapath (400 for
  floating point)
• If an instruction requires more than 4
  microinstructions to implement, control from
  microcode ROM (8000 microinstructions)
• Its complicated!