Chapter Overview
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General Concepts
IA-32 Processor Architecture
IA-32 Memory Management
Components of an IA-32 Microcomputer
Input-Output System
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-1
General Concepts
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Basic microcomputer design
Instruction execution cycle
Reading from memory
How programs run
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-2
Basic Microcomputer Design
• clock synchronizes CPU operations
• control unit (CU) coordinates sequence of execution steps
• ALU performs arithmetic and bitwise processing
data bus
registers
Central Processor Unit
(CPU)
ALU
CU
Memory Storage
Unit
I/O
Device
#1
I/O
Device
#2
clock
control bus
address bus
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-3
Clock
• synchronizes all CPU and BUS operations
• machine (clock) cycle measures time of a single
operation
• clock is used to trigger events
one cycle
1
0
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-4
Instruction Execution Cycle
PC
I-1
memory
op1
op2
fetch
read
registers
registers
write
I-1
write
Fetch
Decode
Fetch operands
Execute
Store output
instruction
register
decode
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program
I-2 I-3 I-4
flags
ALU
execute
(output)
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-5
Multi-Stage Pipeline
• Pipelining makes it possible for processor to execute
instructions in parallel
• Instruction execution divided into discrete stages
Stages
S1
1
S2
S5
I-1
4
I-1
5
I-1
6
7
S6
I-1
3
Cycles
S4
I-1
2
Example of a nonpipelined processor.
Many wasted cycles.
S3
I-1
I-2
8
9
I-2
I-2
10
I-2
11
I-2
12
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
I-2
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Examples
2-6
Pipelined Execution
• More efficient use of cycles, greater throughput of instructions:
Stages
Cycles
S1
1
I-1
2
I-2
3
4
5
S2
S3
S4
S5
S6
For k states and n
instructions, the
number of required
cycles is:
I-1
I-2
I-1
I-2
I-1
I-2
6
7
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
I-1
I-2
I-1
k + (n – 1)
I-2
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Examples
2-7
Wasted Cycles (pipelined)
• When one of the stages requires two or more clock cycles, clock
cycles are again wasted.
Stages
Cycles
S1
S2
S3
exe
S4
1
I-1
2
I-2
I-1
3
I-3
I-2
I-1
I-3
I-2
I-1
I-3
I-1
4
5
6
I-2
7
I-2
8
I-3
9
I-3
10
S5
S6
For k states and n
instructions, the
number of required
cycles is:
I-1
I-1
k + (2n – 1)
I-2
I-2
I-3
11
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
I-3
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Examples
2-8
Superscalar
A superscalar processor has multiple execution pipelines. In the
following, note that Stage S4 has left and right pipelines (u and v).
Stages
S4
Cycles
S1
S2
S3
u
v
S5
S6
1
I-1
2
I-2
I-1
3
I-3
I-2
I-1
4
I-4
I-3
I-2
I-1
I-4
I-3
I-1
I-2
I-4
I-3
I-2
I-1
I-3
I-4
I-2
I-1
I-4
I-3
I-2
I-4
I-3
5
6
7
8
9
10
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
For k states and n
instructions, the
number of required
cycles is:
k+n
I-4
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Examples
2-9
Reading from Memory
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Multiple machine cycles are required when reading from memory,
because it responds much more slowly than the CPU. The steps are:
• address placed on address bus
• Read Line (RD) set low
• CPU waits one cycle for memory to respond
• Read Line (RD) goes to 1, indicating that the data is on the data
bus
Cycle 1
Cycle 2
Cycle 3
Cycle 4
CLK
Address
ADDR
RD
Data
DATA
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-10
Cache Memory
• High-speed expensive static RAM both inside and
outside the CPU.
• Level-1 cache: inside the CPU
• Level-2 cache: outside the CPU
• Cache hit: when data to be read is already in cache
memory
• Cache miss: when data to be read is not in cache
memory.
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-11
How a Program Runs
User
sends program
name to
Operating
system
gets starting
cluster from
searches for
program in
returns to
System
path
loads and
starts
Directory
entry
Current
directory
Program
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-12
Multitasking
• OS can run multiple programs at the same time.
• Multiple threads of execution within the same
program.
• Scheduler utility assigns a given amount of CPU time
to each running program.
• Rapid switching of tasks
• gives illusion that all programs are running at once
• the processor must support task switching.
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-13
IA-32 Processor Architecture
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Modes of operation
Basic execution environment
Floating-point unit
Intel Microprocessor history
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-14
Modes of Operation
• Protected mode
• native mode (Windows, Linux)
• Real-address mode
• native MS-DOS
• System management mode
• power management, system security, diagnostics
• Virtual-8086 mode
• hybrid of Protected
• each program has its own 8086 computer
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-15
Basic Execution Environment
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Addressable memory
General-purpose registers
Index and base registers
Specialized register uses
Status flags
Floating-point, MMX, XMM registers
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
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Addressable Memory
• Protected mode
• 4 GB
• 32-bit address
• Real-address and Virtual-8086 modes
• 1 MB space
• 20-bit address
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-17
General-Purpose Registers
Named storage locations inside the CPU, optimized for
speed.
32-bit General-Purpose Registers
EAX
EBP
EBX
ESP
ECX
ESI
EDX
EDI
16-bit Segment Registers
EFLAGS
EIP
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
CS
ES
SS
FS
DS
GS
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Examples
2-18
Accessing Parts of Registers
• Use 8-bit name, 16-bit name, or 32-bit name
• Applies to EAX, EBX, ECX, and EDX
8
8
AH
AL
AX
EAX
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
8 bits + 8 bits
16 bits
32 bits
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Examples
2-19
Index and Base Registers
• Some registers have only a 16-bit name for their
lower half:
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-20
Some Specialized Register Uses (1 of 2)
• General-Purpose
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EAX – accumulator
ECX – loop counter
ESP – stack pointer
ESI, EDI – index registers
EBP – extended frame pointer (stack)
• Segment
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CS – code segment
DS – data segment
SS – stack segment
ES, FS, GS - additional segments
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-21
Some Specialized Register Uses (2 of 2)
• EIP – instruction pointer
• EFLAGS
• status and control flags
• each flag is a single binary bit
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-22
Status Flags
• Carry
• unsigned arithmetic out of range
• Overflow
• signed arithmetic out of range
• Sign
• result is negative
• Zero
• result is zero
• Auxiliary Carry
• carry from bit 3 to bit 4
• Parity
• sum of 1 bits is an even number
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-23
Floating-Point, MMX, XMM Registers
80-bit Data Registers
• Eight 80-bit floating-point data registers
ST(0)
• ST(0), ST(1), . . . , ST(7)
ST(1)
• arranged in a stack
ST(2)
ST(3)
• used for all floating-point
arithmetic
ST(4)
ST(5)
• Eight 64-bit MMX registers
ST(6)
• Eight 128-bit XMM registers for singleinstruction multiple-data (SIMD) operations
ST(7)
Opcode Register
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-24
Intel Microprocessor History
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Intel 8086, 80286
IA-32 processor family
P6 processor family
CISC and RISC
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-25
Early Intel Microprocessors
• Intel 8080
• 64K addressable RAM
• 8-bit registers
• CP/M operating system
• S-100 BUS architecture
• 8-inch floppy disks!
• Intel 8086/8088
• IBM-PC Used 8088
• 1 MB addressable RAM
• 16-bit registers
• 16-bit data bus (8-bit for 8088)
• separate floating-point unit (8087)
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-26
The IBM-AT
• Intel 80286
• 16 MB addressable RAM
• Protected memory
• several times faster than 8086
• introduced IDE bus architecture
• 80287 floating point unit
Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003.
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Examples
2-27