Instruction Set Architecture

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Instruction Set Architecture

• Chapter 2

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Topics for Discussion

• Review of Chapter 1 introduction
• What is computer organization?
• What will you learn in this course?
• Motherboard
• CPU microprocessor
• Memory
• Instruction set architecture
• Stored program computer
• Interface between software and hardware
• Instructions
• Design principles
• Instructions, registers, and memory
• Simple instructions types and formats

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Computer Organization

• Is the study of major components of a modern
  digital computer, their organization and
  assembly, and the architecture and inner workings
  of these components.
• It also deals with design principles for a good
  performance.

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What will you learn in this course?

• How are high level language (HLL) translated to
  the language of the hardware.
• How does hardware execute instructions?
• What is the interface between hardware and
  software?
• How does the software instruct (or control) the
  hardware to perform the needed function?
• What determines the performance of a program?
• How can a program improve performance?
• Original program, its translation, effectiveness
  of the hardware, other special techniques such as
  pipelining
• What techniques can by hardware designers to
  improve performance?

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Mother Board

• Figure 1.10
• Contains packages of integrated circuit chips (IC
  chips) including a processor, cache (several),
  memory (DRAM), connections for IO devices
  (networks, disks)

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Central Processing Unit (CPU)

• See Fig 1.9
• Example Intel 80386? 80486?Pentium
• Main components of a CPU are datapath and
  control unit
• Datapath is the component of the processor that
  performs (arithmetic) operations
• Control is the component of the processor that
  commands the datapath, memory , IO device
  according to instruction of the program
• Cache provides but fast memory that acts as a
  buffer for slower /larger memory outside the chip.

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IC chip manufacturing process

• Lets discuss Fig. 1.14 and 1.15
• Silicon is a semiconductor by adding appropriate
  elements, it can be turned into a conductor,
  insulator or can be made to switch between the
  two.

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Instruction set Architecture

• An important abstraction between hardware and
  software.
• Lets discuss this concept.
• Computer operation is historically called an
  instruction.
• Instructions stored similar to data in a memory
  give rise to an important foundational concept
  called the stored program computer.

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C to MIPS instruction
Design principle 1 simplicity favors
regularity In the above example all instructions
have 3 operands
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Register set

• Where do the data get stored in the CPU?
• Named locations called registers? How many?
  Typical small compared to memory sizes.
• Registers MIPS-32 has 32 register
• Denoted by s0, s1, etc. s0, s5
• Temporary registers are denoted by t0, t1

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C to MIPS instruction (Take 2 with registers)
Design principle 2 Smaller is faster Memory
available as registers is 32 in number
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Memory Operations

• Data and instructions are stored in memory
  outside the CPU.
• Data is loaded from memory and stored in memory.
• Load word (lw)
• Store word (sw)
• 32 resgiters
• 230 words or 232 addressable locations or bytes

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C language to Memory instructions
Base register concept base register is s3 and
Offset of 32 for 8 words and offset of 48 for 12
words
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Instruction Types

• add and sub
• lw and sw
• Now lets see how we can deal with a constant
  value data.
• Consider C language statement x x 4
• Too complex
• lw t0, AddrConst(s1)
• add s3,s3,t0
• Instead how about
• addi s3,s3,4
• Summary is in Fig.2.4
• Design principle 3 Make the common case fast.
  Example addi instead of add an constant from
  memory.

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Instruction format R type
Can we use the same format for addi and add? Then
we will Have only 11 bit constant
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Instruction format I type
Design principle 4 good design demands good
compromise Keep instruction length same needing
different formats I and R type are examples
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Summary

• Figure 2.7 very nicely summarizes all we learned
  so far.
• MIPS operands
• MIPS memory
• MIPS Assembly language
• MIPS instructions type and formats
• And of course, the four design principles.