T-61.123 Computer Architecture

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T-61.123 Computer Architecture

• Target
• Understanding how a computer works
• how is the data processed how is the processing
  controlled
• how is the data stored in the memory
• how is the data input and output
• how to measure performance what affects
  performance

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Course Administration

• Instructor Dr. Seppo Haltsonen
  (seppo.haltsonen_at_evtek.fi)
• Assistants NN (tark_at_hut.fi)
• Project SPIM simulator...
• Registration wwwTopi!
• Materials Delivered via Otapaino
• Newsgroup opinnot.tik.tark

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Course Administration

• 11 lectures on Thursdays at 16.15
• 6 tutorial sessions, extra points available
• Course assistants
• give all kind of help
• reception time and place announced later
• can be best contacted by e-mail

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Assessment

• exam grade 2/3 project grade
  1/3
• course grade
• Exam contains 5 problems, max 6 points each to
  pass one has to get at least 12 points
• If the project is late, its grade is reduced

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Project

• Deals with MIPS instruction set architecture
• The project is personal
• Deadline is 1st December
• The report has to be returned by e-mail

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Expected Previous Knowledge

• Basic knowledge of computers
• Basic knowledge of programming
• instructions, program structures
• Fundamentals of computer technology
• gates, flip-flops, combinational circuits,
  registers, sequential circuits

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Textbook

• David A. Patterson and John L. Hennessy, Computer
  Organization Design The Hardware/Software
  Interface, 2nd Edition, Morgan Kaufmann, 1998
• Need 2nd Edition? Yes!
• gtgt 50 text changed, all exercises changed, all
  examples modernised, new sections, ...

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Support Materials

• http//www.mkp.com/cod2e.htm
• Web extensions of the books content
• Three sets of lecture slides
• SPIM simulator
• Lecture slides are mostly based on the above
  slide sets (especially those of Tod Amon)

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What computers are

• Computers are programmable electronic devices.
• They solve problems using algorithms.
• They consist of hierarchical layers of hardware
  and software.

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An algorithm

• Compute the average age of a group of people.
• 1. n number of people input
• 2. sum 0
• 3. i n
• 4. sum sum age of person i input
• 5. i i-1
• 6. if i gt 0 then go to 4
• 7. sum sum/n
• 8. average age sum output

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What is involved in an algorithm?

• data (operands and results)
• operations
• control (order of operations)

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Hardware layers

• structures on silicon or other materials
• electronic components (transistors etc.)
• logic components (gates, flip-flops)
• logic circuits (adders, registers, counters,
  etc.)
• functional units (ALU, multiplier, shifter,
  register file, control unit)
• computer components (CPU, memory, I/O unit)
• computer system

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Software layers

• Machine language
• 0010 1011 1101 1000
• 1001 0111 0101 1110
• Assembly language
• MOV A, 3CH
• ADD A, 20H
• High-level language
• y 15
• x (yy-5, 30/y)

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Abstractions

• hardware or software layers are called
  abstractions
• abstractions are a way to cope with complexity
• lower-level details are hidden to offer a simpler
  model at higher levels

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Definition one

• Computer architecture
• attributes of a system visible to a programmer
  instruction set, data types, I/O mechanisms,
  addressing of memory
• Computer organisation
• hardware details transparent to a programmer
  operational units and their interconnections,
  peripheral interfaces, memory technology

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An example

• architectural issue has the computer a multiply
  instruction or not?
• organisational issue has the computer a special
  multiply unit or does it repeatedly use the add
  unit?

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Definition two

• Computer architecture
• Instruction set architecture
• Machine organisation
• Instruction set architecture interface between
  the hardware and low-level software

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Instruction set architecture

• Organisation of storage registers, memory
• Representations of data
• Instruction set
• Instruction formats
• Modes of addressing and accessing data
• Exceptional conditions

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Instruction set architecture

• Advantage enables different implementations of
  the same architecture
• Disadvantage may prevent using new innovations

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Machine organisation

• Implementation, capabilities and performance
  characteristics of functional units
• Interconnections of these units
• Information flows between these units
• Control of information flow
• VHSIC Hardware Description Language (VHDL)
  descriptions

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Block diagram of a computer
CPU
ALU
Input Unit
Output Unit
Control Unit
Register Unit
Memory
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Computer blocks

• ALU calculations
• Register unit data, memory addresses
• Control unit control of the whole computer
• Memory data, programs
• I/O unit communication with the surroundings

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Instruction cycle

• Fetch instruction
• Decode instruction
• Fetch operands
• Execute operation
• Store result
• Locate next instruction

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Instruction fetch
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Technology changes

• vacuum tube ? transistor ? IC ? VLSI
• Moores law number of transistors on a single
  chip doubles every 1.5 years
• Consequences of Moores law (and other
  improvements)
• processor performance and memory capacity double
  every 1.5 years
• computers get smaller, faster and cheaper

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Contents of the course

• Performance issues
• MIPS instruction set architecture
• Datapath (ALU)
• Control
• Memory hierarchy
• I/O interface