Intel Ia32

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Intel IA32 (80x86)

Microprocessors

Dr. Doug L. Hoffman

Computer Science 330Spring 2002

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A Classic CISC

Microprocessor

The 80x86 family of Microprocessors is the

dominant PC processor architecture:

Around since 1978.

Continually enhanced for two decades.

Takes Upward compatibility to an extreme.

Started as a Modified Accumulator Architecture. Now a General Purpose Register-Memory Architecture (sort

of).

Over 400,000,000 have been sold.

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History of the 80x86

Intel 4004 (4 bit) and 8008 (8 bit)accumulator architecture embedded

control processors. Early 1970s. Intel 8080, and enhanced 8 bit processor

that found its way into some of the first

commercial PCs. Also a straightforwardaccumulator architecture. Mid 1970s.

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Intel 8086, 16 bit assembly-languagecompatible extension of the 8080

architecture. 1978. All registers 16 bits wide.

Additional registers all have dedicated uses.

Extended Accumulatorarchitecture.

IBM selects the 8088, an 8086 with an 8bit external bus, as the processor for theIBM PC. Early 1980.

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Intel 8087 floating-point coprocessor adds~60 new instructions to the 8086

instruction set. 1978. All floating-point instructions processed on the coprocessor chip.

Additional registers arranged as a stack to avoid makinginstructions even longer (and avoid changes to the 8086).

Adds 8 80 bit floating-point registers arranged as a stack.

Hardware designers decided to handle stack overflow/underflowin software. This never worked, resulting in a 50% reduction inFP performance.

Extended Stackarchitecture.

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Intel 80286 further extends thearchitecture by increasing the address

space. 1982.

Expanded memory address space from 20 bits to 24 bits.

Added memory mapping and multilevel protection scheme (see

book). Added new instructions to support memory management.

Added real addressingmode to support legacy 8086 code.

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Intel 80386 moves up to 32 bitarchitecture. 1985.

Additional registers (segment pointers).

All GP registers now 32 bits.

Address space now 32 bits with several new addressing modes.

Added paging support under existing segmented architecture. Almost a general purpose register machine.

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Intel 80486 basically improvesperformance. 1989.

Intel Pentium, 1992, and P6, 1995, alsoimprove performance and addmultiprocessor support (only four new

instructions. Since then more versions than you can

sensibly keep track of.

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Intel CPU Specs

There are a large number of processor models

and packages available from Intel.

Celeron, Pentium II, Pentium III, Pentium 4.

Slot 1, Socket 370, Socket 7, etc.

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Intel CPU Specs, cont.

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Intel CPU Specs, cont.

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Instruction Set Madness

The x86 isnt all that complex -- it just doesnt make a lot of sense, Mike Johnson, AMD

Almost all registers have dedicated uses; stack

pointers, data segment pointers, index register, etc,

depending on mode.Segmented address space plus page translation.Instructions can be from 1 to 17 bytes long.Addressing mode use seemingly haphazardly

applied to instructions. Definitely not orthogonal.Weird, half baked stack architecture for FP.

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Registers of the 8086CPU8 General Purpose 16 bit Registers

Four 16-bit registers can be divided into two 8-bit registers

AX = AH|AL - Accumulator (Accumulator High|Accumulator Low)

BX = BH|BL - Base (High|Low)- can be used as "pointer"

CX = CH|CL - Count (High|Low) - used for counting loops

DX = DH|DL - Data (High|Low) - paired with AX for "combined" 32-

bit register. DX is high word, AX is low word.

Four 16-bit registers used for Indexing and Stack

SI - Source Index - used for indirect addressing

DI - Destination Index - used for indirect addressing

SP - Stack Pointer - accesses Stack Segment

BP - Base Pointer

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Registers of the 8086CPU6 Special Purpose Registers

CS (Code); DS (Data); ES (Extra); (SS) Stack segment registers

IP - Instruction Pointer holds address of next instruction

Flag Register - OF|DF|IF|TF|SF|ZF|AF|PF|CF "flag" bits

Overflow Flag set if last operation caused "signed overflowed"

Sign Flag set if last operation was negativeZero Flag set if last operation resulted in 0

Carry Flag set if last operation had carry out

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Registers of the 8086CPUMemory Address Spaces

CS:IP pair points to code address space

DS:offset points to data address space

SS:SP pair points to stack address space

ES: extra data address spaceFS:GS even more extra data segment pointers add in 386.

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Pentium III Architecture

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Pentium III Die

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Send in the Clones:AMD Athlon

frequently used instructions extremely fast (typically in one clock).

Less common or very complex instructions need to be decoded in a

slower process (usually >2). AMD calls these OPs 'MOps', for Macro

Operations.

dispatch 9 Ops at the same time (Pentium only 5)

256 kB L2 cache running on a backside bus at CPU clock speed.

128 kB L1 cache, 64 kB data and 64 kB instruction cache.

3 (three!) out-of-order, fully parallel FPU pipelines.Much RISC-ier core than Pentium III.

Intel can only supply 60% of the market due to capacity limits.

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Send in the Clones: Via Cyrix III

Developed by National Semiconductor133 MHz Front Side Bus (although it supports 66 MHz, and 100 MHz

FSB).256 KB integrated L2 cache along with a 64 KB integrated L1 cache.

3dNow! SIMD instructions in a dual pipelined FPU.As with the MII, the Cyrix III supports MMX.superscalar design featuring two seven stage pipelines allowing two

processing streams to be processed simultaneously.two level translation buffer and a 512 entry branch target buffer.

out-of-order execution through register renaming and data forwarding andbypassing to resolve data dependencies between pipelines.Speculative execution after a predicted branch is also supported.15% to 20% cheaper than a comparable Celeron.Hope to capture 10% of market.

Subject of a lot of legal action by Intel but VIA is still in business.

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Send in the Clones: Via Cyrix III

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Intels Latest: The Pentium 4 2.4GHz

478 pin packaging

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The newer Pentium 4 chips, with their 512K L2 caches,

perform extremely well, peaking out at nearly 900 MFLOPS at larger

matrix sizes than the Athlon XP.

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Conclusions:

The Pentium 4 is faster at some things, and the Athlon XP is faster at others.

On balance, the two processors are very closely matched.

"Which is fastest?" depends entirely on what it is you want to do.Tech-report.com

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And The Future Belongs to...

Itanium

The IA64 processor previously known as Merced

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The Last Word

Intel added new features to the originalinstruction set as you might add clothing

to a packed bag, P & H.

I dont really want onebut I have a half dozen.

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Intel Ia32