An Introduction to IA-32 Processor Architecture Eddie Lopez CSCI 6303 Oct 6, 2008

Overview Microcomputer Design Intel IA-32 Family Tree Operating Environment Input / Output The Future

What is IA-32? Intel Architecture 32-bit Also known as x86 or i386 Intel chip released in 1985 First Intel 32-bit chip Backward Compatibility preserved Replaced 16-bit architecture of 8086,80186, Microcomputer Design

Other Manufacturers also produced IA-32 compatible processors AMD, Cyrix, VIA Microcomputer Design

The Central Processing Unit (CPU)

Microcomputer Design Motherboard

Microcomputer Design CPU Heat Sinks

Microcomputer Design The Central Processing Unit contains: Control Unit Arithmetic Logic Unit (ALU)‏ High Frequency Clock Registers

Microcomputer Design

IA-32 Instruction Execution Pipeline: Bus Interface Unit – accesses memory Code Prefetch Unit – instruction queue Instruction Decode Unit – translates to microcode Execution Unit – executes microcode Segment Unit – translates logical addresses to linear addresses Paging Unit – translates linear addresses to physical addresses.

Microcomputer Design Instruction Execution Cycle Fetch – gets instruction from memory Decode – translate into microcode Fetch input – get data from memory Execute – ALU performs instruction Store output – store data back into memory

Questions?

IA-32 Architecture Microcomputer Design Intel IA-32 Family Tree Operating Environment Input / Output The Future

IA-32 Family Tree 8086 (1979) Segmented Memory 20 bit addressing 1 MB limit

IA-32 Family Tree (1982) Protected Mode Privilege Rings Ring 0 – Kernel Ring 1 – OS / Device Drivers Ring 2 – Device Drivers Ring 3 - Applications

IA-32 Family Tree (1985) Intel’s First 32-bit Processor Flat Memory Model 32-bit Addressing 4 GB Limit Paging

IA-32 Family Tree (1989) Level 1 Cache (8 KB) On-board FPU (Floating Point Unit) 5 Stage Pipeline

IA-32 Family Tree Pentium (1993) Super Scalar (u,v pipelines) Separate Code and Data Cache (8KB) Branch Prediction

IA-32 Family Tree Branch Prediction Model Loop 100 times Do something Next loop Next instruction

IA-32 Family Tree Pentium Pro (1995) 3 instruction pipelines Out of order execution 36-bit address bus can address 64GB memory 256kb Level 2 cache MMX Instruction Set

IA-32 Family Tree Pentium II (1997) Level 1 cache increased 16KB each Level 2 cache 256KB, 512KB, 1 MB Celeron 128 KB (Value Market)

IA-32 Family Tree Pentium III (1999) SSE instruction set (XMM registers)‏ Pentium IV (2000) SSE2 instruction set NetBurst Micro-architecture Hyper-Threading

IA-32 Family Tree NetBurst Micro-Architecture ALU runs at x2 speed Dynamic Execution Out-Of-Order

IA-32 Family Tree Core Micro-Architecture 4 Pipelines (14 stages) 3 ALU Units 4 Instruction Decoders Macrofusion

IA-32 Family Tree Core Micro-Architecture (Intel Conroe)

Questions?

Overview Operating Environment Operating Modes Registers Memory Management Instruction Format

Operating Modes Real Mode Protected Mode System Management Mode Virtual 8086 Mode

Operating Modes Real Mode Operating mode for bit addressing: 1MB of memory No memory protection or multitasking Modern chips start up in real-mode for backward compatibility

Operating Modes Protected Mode Introduced in Intel chip 32-bit addressing: 4GB of memory Flat memory model Uses privilege rings (0-3) to regulate applications.

Operating Modes Protection Rings

Operating Modes Virtual 8086 Mode Allows “real mode” programs to run under the supervision of a protected mode operating system Allows operating systems to run Virtual DOS machines to run legacy software.

Operating Modes System Management Mode Provides OS with power management and system security functions.

Registers What is a register? Storage space on the CPU Used for fast memory storage and processing Each of the general registers has a special name and a specific use.

Registers

Floating Point registers (80-bit)‏ ST0 – ST7 (Part of Floating Point Unit)‏ MMX registers (64-bit)‏ MMX0 – MMX7 SIMD registers (128-bit)‏ XMM0 – XMM7 Control Registers (32-bit)‏ CR0 - CR4

Registers Test Registers TR4 - TR7 Description Registers GDTR, LDTR, IDTR Task Register TR Control Registers (32-bit)‏ CR0 - CR4

Registers MMX Multi-Media Extensions Introduced on the Pentium Pro Used for graphics and multimedia SSE Streaming SIMD Introduced on the Pentium III One instruction can be applied to multiple data

Registers 6 Segment Registers (16 bit) contain address pointers to segments of the currently running process CSCode Segment DS, ES, FS, GSData Segments SSStack Segment 1 Instruction Pointer (32-bit)‏ Contains the memory address of the next instruction to execute.

Registers Compatibility with previous architecture To allow backward compatibility, registers EAX, EBX, ECX, and EDX can be addressed as subsets. Example using the EAX register:

Registers Roles for Generic Registers EAX – Accumulator EBX – Base Addressing ECX – Counter EDX – Data Operand EDI – Destination Address ESI – Source Address ESP – Stack Pointer EBP – Stack Base Pointer

Registers EFLAGS register Carry Flag (CF) – Unsigned Carry Overflow Flag (OF) – Signed Overflow Sign Flag (SF) - Negative arithmetic results Zero Flag (ZF) – Zero arithmetic results Auxiliary Carry Flag Parity Flag – Even/Odd of a value

Instruction Set IA-32 Architecture uses CISC CISC – Complex Instruction Set Computer Large amount of complex instructions Easier for compilers and programmers But placed a strain on decoder Backward Compatibility is a burden RISC Reduced Instruction Set Computer Atomic instructions Easy to decode and run quickly

Instruction Format Instructions of varying length Design decisions from 8086 have placed a burden on modern architecture. One instruction can vary from 1 byte to 17 bytes

Instruction Format The instruction Format Prefix (0-4 bytes)‏ Opcode (1-3 bytes)‏ R/M Modifier (0-1 byte)‏ SIB Modifier (0-1 byte)‏ Displacement Modifier (0-4 bytes)‏ Data elements (0-4 bytes)‏

Instruction Format Prefix (0-4 bytes)‏ Alerts the CPU that address or operand sizes are about to change Opcode (1-3 bytes)‏ The operation to execute. Common operations have one byte code, less frequently used ones get three opcodes R/M Modifier (0-1 byte)‏ Specifies the addressing mode – Register or Memory

Instruction Format Scale / Index / Base (0-1 byte)‏ Indicates whether the register serves as an index or a base and gives the scale factor Displacement Modifier (0-4 bytes)‏ Provides an additional data offset Data elements (0-4 bytes)‏ Immediate data (values and addresses)‏

Instruction Sets Types of instructions in the set: Move data between memory and registers Exchanging data Integer Arithmetic Flow Control Procedure call and return Manipulating the stack Character string operations

Memory Management Real Mode 20 bit Addressing: 1 MB of memory Addresses: to FFFFF Memory is logically divided into 64KB segments Segment registers stored the segment CPU converts segment:offset value to its linear equivalent

Memory Reading From Memory Fetching operands from RAM is slow Bus Interface Unit polls RAM for data and waits. The CPU is goes into a wait state. Requires many clock cycles depending on speed of RAM. Level-1 cache is much faster – keeps data near Registers are the fastest

Memory Reading From Memory Processor places address on the address bus Processor asserts the memory read control signal Processor waits for memory to place the data on the data bus Processor reads the data from the data bus Processor drops the memory read signal

Memory Management Protected Mode 32 bit Addressing: 4 GB of memory Addresses: to FFFFFFFF Each process “sees” the full 4 GB. Segment registers store indexes to a global descriptor table. Multiple processes running simultaneously Prevents processes from corrupting each other's data.

Memory Management Paging Segments are divided into 4KB blocks Virtual Memory Manager Blocks are sent to the page file on the hard disk when they are not in use Switching between applications in low memory condition requires a delay The more memory, the less paging is required

Program Execution What happens when program runs? User clicks on a program icon Operating System (OS) searches for program OS loads programs into available memory What happens if memory is full? OS Allocates blocks of memory and adjusts pointers in the code to point to the data OS branches to the first executable instruction At this point, it becomes a Process Memory is released after program ends

Program Execution Multi-tasking OS can run multiple processes Only one process runs at any given time Processes run in a time slice CPU must support Task Switching Task Switching requires that all registers and program counter be stored when switching to another process

Questions?

IA-32 Architecture Microcomputer Design Intel IA-32 Family Tree Operating Environment Input / Output The Future

Input / Output Input Keyboard, Mouse, Network Card, etc Output Monitor, Printer, etc

Input / Output There are 4 access levels of I/O interaction Level 3 – High level programming language Level 2 – Operating System API Level 1 – BIOS Level 0 – Direct Hardware interaction The lower the access level, the faster the result, but what is the trade-off? Operating System may reserve direct access to hardware

Input / Output Input/Output is Interrupt Driven What happens when you press a key on the keyboard? Keyboard sends signal to CPU CPU stops and handles the request by the keyboard that a key was struck CPU puts keystroke into a buffer and returns to the previous process

The Future Intel 64 Shrinking Cores 45 nm core (Intel Penryn) 32 nm (Intel 2009) Multiple Cores Xeon 7400 Hexcore (9/16/08) IA-32 phase-out

Questions? The End…