William Stallings Computer Organization and Architecture 8th Edition

1
William Stallings Computer Organization and
Architecture8th Edition

• Chapter 10
• Instruction Sets
• Characteristics and Functions

Felipe Navarro Luis Gomez Collin Brown
2
What is an Instruction Set?

• The complete collection of instructions that are
  understood by a CPU
• Machine Code
• Binary
• Usually represented by assembly codes

3
Elements of an Instruction

• Operation code (Op code)
• Do this
• Source Operand reference
• To this
• Result Operand reference
• Put the answer here
• Next Instruction Reference
• When you have done that, do this...

4
Instruction Cycle State Diagram
5
Instruction Representation

• In machine code each instruction has a unique bit
  pattern
• For human consumption (well, programmers anyway)
  a symbolic representation is used
• e.g. ADD, SUB, LOAD
• Operands can also be represented in this way
• ADD A,B

6
Simple Instruction Format
7
Instruction Types

• Data processing
• Data storage (main memory)
• Data movement (I/O)
• Program flow control

8
Number of Addresses (a)

• 3 addresses
• Operand 1, Operand 2, Result
• a b c
• May be a forth - next instruction (usually
  implicit)
• Not common
• Needs very long words to hold everything

9
Number of Addresses (b)

• 2 addresses
• One address doubles as operand and result
• a a b
• Reduces length of instruction
• Requires some extra work
• Temporary storage to hold some results

10
Number of Addresses (c)

• 1 address
• Implicit second address
• Usually a register (accumulator)
• Common on early machines

11
Number of Addresses (d)

• 0 (zero) addresses
• All addresses implicit
• Uses a stack
• e.g. push a
• push b
• add
• pop c
• c a b

12
How Many Addresses

• More addresses
• More complex (powerful?) instructions
• More registers
• Inter-register operations are quicker
• Fewer instructions per program
• Fewer addresses
• Less complex (powerful?) instructions
• More instructions per program
• Faster fetch/execution of instructions

13
Instruction Set Design

• Operation repertoire
• How many ops?
• What can they do?
• How complex are they?
• Data types (Characteristics later)
• Different forms of data to which operations are
  performed
• Instruction formats
• Length of op code field
• Number of addresses
• Size of various fields

14
Instruction Set Design (cont.)

• Registers
• Number of CPU registers available
• Which operations can be performed on which
  registers?
• Addressing modes (later)
• RISC vs. CISC

15
Types of Operand

• Addresses
• Numbers
• Integer/floating point
• Characters
• ASCII etc.
• Logical Data

16
Types of Operation

• Data Transfer
• Arithmetic
• Logical
• Conversion
• I/O
• System Control
• Transfer of Control

17
Data Transfer

• Specify
• Source
• Destination
• Amount of data
• Addressing mode (later)
• May be different instructions for different
  movements
• e.g. IBM 390
• Or one instruction and different addresses
• e.g. VAX

18
Arithmetic

• Add, Subtract, Multiply, Divide
• Signed Integer (Always provided for)
• Floating point (Often provided for)
• Packed decimals (Often provided for)
• May include
• Increment (a)
• Decrement (a--)
• Absolute Value (a)
• Negate (-a)
• May involve data transfer operations

19
Logical

• Bitwise operations
• AND, OR, XOR, NOT, Equals

Conversion

• Ex Binary to Decimal. Decimal to Binary

20
Input/Output

• Falls into the following categories
• Control and timing
• Processor communication
• Device communication
• Data buffering
• Error detection
• May be specific instruction
• May be done using data movement instructions
  (memory mapped)
• May be done by a separate controller (DMA)

21
Systems Control

• Executed only in a privileged state
• CPU needs to be in specific state
• Ring 0 on 80386
• Kernel mode
• For operating systems use

22
Transfer of Control

• Branch
• e.g. branch to x if result is zero
• Skip
• e.g. increment and skip if zero
• ISZ Register1
• Branch xxxx
• ADD A

23
Branch Instruction
24
Nested Procedure Calls
25
Use of Stack
26
Stack Frame Growth Using Sample Procedures P and Q
27
Byte Order(A portion of chips?)

• What order do we read numbers that occupy more
  than one byte
• e.g. (numbers in hex to make it easy to read)
• 12345678 can be stored in 4x8bit locations as
  follows

28
Pentium call/return Instruction

• Provide four instructions to support procedure
  call/return
• CALL
• ENTER
• LEAVE
• RETURN
• A new Procedure call/return
• Push the return point on the stack
• Push the current frame pointer on the stack
• Copy the stack pointer as the new value of the
  frame pointer
• Adjust the stack pointer to allocate frame

29
Byte Order (example)

• Address Value (1) Value(2)
• 184 12 78
• 185 34 56
• 186 56 34
• 186 78 12
• i.e. read top down or bottom up?

30
Byte Order Names

• The problem is called Endian
• The system on the left has the least significant
  byte in the lowest address
• This is called big-endian
• The system on the right has the least
  significant byte in the highest address
• This is called little-endian

31
Example of C Data Structure
32
Alternative View of Memory Map
33
Questions

• 1 What are the typical elements of a machine
  instruction?
• 2 What types of locations can hold source and
  destination operands?
• 3 If an instruction contains four addresses, what
  might be the purpose of each address?
• 4 What types of operands are typical in machine
  instruction set?
• 5 What is the difference between an arithmetic
  shift and a logic shift?
• 6 What is the difference between assembly
  language and machine language
• 7 What is the difference between big endian and
  little endian?
• List three places for storing the return address
  for a procedure return.

34
Answers

• 1 Operation code, source operand reference,
  result operand reference and next instruction
  reference.
• Register and memory.
• Two operands, one result, and the address of the
  next instruction.
• Address, character, numbers and logical data.
• In logical shift, the bits of word are shifted
  left or right. Arithmetic shift treats the data
  as a signed integer and does not shift the sign
  bit.

35
Answers (cont.)

• 6 Assemble language uses symbolic names for
  addresses that are not fixed to specific physical
  address this is not the case with machine
  language.
• A multibyte numerical value stored with the most
  significant byte in the lowest numerical address.
  A multibyte numerical value stored with the most
  significant byte in the highest numerical
  address.
• Register, start of procedure, top of stack