AKT211 – CAO

04 – x86 Architecture: Intel 8088

GhifarParahyangan Catholic University

Sept 19, 2011

Reference• Brey, Barry. “The Intel Microprocessor

8086/8088, 80186/80188, 80286, 80386, 80486, Pentium, and Pentium Pro Processor: Architecture, Programming, and Interfacing 4th edition”. Prentice-Hall International Inc. 1997

Outline Intel x86 Architecture Evolution The Programming Model Register Types Instruction Set Data Types Byte ordering Memory Organization

Intel x86 Arch. Evolution• 8080

– The world’s 1st general-purpose microprocessor– 8-bit machine– 8-bit data path to memory– Altair

• 8086– 16-bit machine– wider data path, larger register– instruction cache / queue– 1st appearance of the x86 architecture– The variant : 8088, IBM’s 1st personal computer– 1-MByte memory addressing

Intel x86 Arch. Evolution• 80286

– extension of 8086, enabled addressing a 16-MByte

• 80386– Intel 1st 32-bit machine– support multitasking

• 80486– more sophisticated and powerful cache

technology– sophisticated instruction pipelining– built-in math coprocessor

Intel x86 Arch. Evolution• Pentium

– use of superscalar technology, allow multiple instructions to execute in parallel

• Pentium Pro– aggressive use of register renaming– branch prediction, data flow analysis, speculative

execution• Pentium II

– Intel MMX technology, designed to process video, audio, and graphic data efficiently

• Pentium III– additional floating-point instructions to support 3D

graphics software

Intel x86 Arch. Evolution• Pentium 4

– Addition floating-point and other enhancements for multimedia

• Core– The 1st Intel x86 microprocessor with a dual core:

the implementation of two processor on a single chip

• Core 2– extends to 64-bit– Core 2 Quad provides 4 processors on a single

chip

The Programming Model of Intel

Register Types1. General-purpose/multipurpose

register EAX, EBX, ECX, EDX, EBP, EDI, ESI

2. Special-purpose register EIP, ESP, EFLAGS

3. Segment register CS, DS, ES, SS, FS, GS

General-Purpose Register• EAX (accumulator)

– 32-bit register (EAX), as a 16-bit register (AX), or as either of two 8-bit registers (AH and AL)

– used for instructions such as addition, subtraction, multiplication, division, and some of adjustment instructions

– in 80386 above, it may also hold the offset address of a location in the memory system.

• EBX (base index)– 32-bit register (EBX), as a 16-bit register (BX), or

as either of two 8-bit registers (BH and BL)– hold the offset address of a location in the

memory system– in 80386 above, it also can address memory data

General-Purpose Register

• ECX (counter)– hold the count for various instructions: repeated

string instructions (REP/REPE/REPNE), shift, rotate, and LOOP/LOOPD

– in 80386 above, it also can hold the offset address of memory data

• EDX (data)– holds a part of the result from a multiplication or

part of the dividend before a division• EBP (base pointer)

– points to a memory location for memory data transfer

General-Purpose Register

• EDI (destination index)– addresses string destination data for the string

instructions• ESI (source index)

– addresses source string data for the string instructions

Special-Purpose Register

• EIP (instruction pointer)– addresses the next instruction in a section of

memory defined as code segment– used to find the next sequential instruction in a

program located within the code segment– can be modified with a jump or a call instruction

• ESP (stack pointer)– addresses an area of memory called stack– stack memory stores data through this pointer

• EFLAGS– indicate the condition of the microprocessor as

well as control its operation

EFLAG and FLAG register (8086 Pentium)

EGLAG and FLAG register (8086 Pentium)

• C (carry)– holds the carry after addition of the borrow after

subtraction– also indicates error conditions as dictated by

programs and procedures• P (parity)

– a count of ones in a number expressed as even or odd

– 0: odd parity, 1: even parity– E.g.: If a number contains 3 binary one bits, it has

odd parity. If a number contains zero one bits, it has even parity

EGLAG and FLAG register (8086 Pentium)

• A (auxiliary carry)– holds the carry (half-carry) after addition of the

borrow after subtraction between bits position 3 and 4 of the result

– used only by the DAA and DAS instructions to adjust the value of AL after a BCD addition or subtraction.

• Z (zero)– shows that the result of an arithmetic or logic

operation is zero– 1: zero, 0: not zero

• S (sign)– holds the arithmetic sign of the result after

execution– 1: sign, 0: unsigned (positive)

EGLAG and FLAG register (8086 Pentium)

• T (trap)– enables trapping through an on-chip debugging

feature– 1: interrupts the flow of the program– 0: trapping/debugging feature is disabled

• I (interrupt)– control the operation of the INTR (interrupt

request) input pin• D (direction)

– select either the increment or decrement mode for the DI and/or SI registers during string instruction

EGLAG and FLAG register (8086 Pentium)• O (overflow)

– indicates that the result has exceeded the capacity of the machine

• IOPL (I/O privilege level)• NT (nested task)• RF (resume)• VM (virtual mode)• AC (alignment check)• VIF (virtual interrupt flag)• VIF (virtual interrupt pending)• ID (identification)

Segment Register• CS (code)

– holds the code (programs and procedures) used by microprocessor, defines the starting address of the section of memory holding code

• DS (data)– contains most data used by a program– accessed by an offset address

• ES (extra)– used by some of the string instructions to hold

destination data• SS (stack)

– defines the area of memory used for the stack• FS & GS (stack)

– allow 2 additional memory segments for access by programs (80386 above)

Memory Organization

Instruction Set• Data moving instructions.• Arithmetic - add, subtract, increment, decrement,

convert byte/word and compare.• Logic - AND, OR, exclusive OR, shift/rotate and

test.• String manipulation - load, store, move, compare

and scan for byte/word.• Control transfer - conditional, unconditional, call

subroutine and return from subroutine.• Input/Output instructions.• Other - setting/clearing flag bits, stack

operations, software interrupts, etc.

Types of Operands• Addresses• Numbers

– Integer/floating point• Characters

– ASCII etc.• Logical Data

– Bits or flags• (Aside: Is there any difference between numbers and

characters? Ask a C programmer!)

Data Types in x86

General Data Types• 8 bit (Byte)• 16 bit (word)• 32 bit (double word)• 64 bit (quad word)• 128 bit (double quadword)• Addressing is by 8 bit unit• Words do not need to align at even-

numbered address• Data accessed across 32 bit bus in units of

double word read at addresses divisible by 4• Little endian

Numeric Data Types

Memory Organization• generally consists of program,

data, stack• their memories occupy the same

memory space• Total addressable memory size :

1 MB

Byte Ordering• 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

Byte Ordering• Big Endian

– Left Right– Most significant byte in

the lowest numerical byte address

• Little Endian– Right Left– Least significant byte in

the lowest numerical byte address

C Data Structure to Endian Mapping

Any Question ?

Assignment 2• Find the latest paper about

research related to the recent processor technology and review it

• Collect your review in hardcopy form at mid-semester test

THANK YOU