80286,80386 and 80486

Advanced Microprocessors

Introduction80286 is an first advanced Processor with

Memory management unit and Protection abilities

24 bit address bus available which can address 16 Mbytes of Physical memory

It runs with 12.5Mhz clock frequency It is compatible with its predecessors like 8086

and 8088 processorsIt works in 2 operating modes like

Address mode &Virtual Address mode

Real Address mode: 80286 can address up to 1Mb of physical memory address like 8086

Virtual Address mode:it can address up to 16 Mb of physical memory address space and 1 Gb of virtual memory address space

In real address mode, the 80286 is object code compatible with 8086.

In protected virtual address mode, it is source code compatible with 8086

Architecture of 80286

Comparison between 8086 and 80286 8086 Intel 8086 was developed in

1978 It has almost 3000 different

instruction for programming Peripheral ICs are not available

on board Operating frequencies are

between 5 to 10MHz No memory management

capability 20 bit address line, which can

access 2^20=1MB memory 8086 operates in Real

addressing mode Slow performance compared

with 80286 . Push and pop instructions are

used to store in stack memory

80286 Intel 80286 was developed 1983 More instructions available

compared to 8086 Peripheral ICs are available on

Board Operating frequencies are

between 8 to 12.5MHz 80286 has memory

management capability that maps 2^30 (1GB) virtual memory

Operates in Real mode and protection mode

808286 is high speed processor compared with 8086. almost 6 times

Push , pop and push immediately instructions are availabe

Features of 80386 It is an 32 bit processor that supports 8,16 and 32-bit operands. It has 32 bit registers , 32 bit internal and external bus and 32

bit address busDue to 32 bit address bus, it can address up to 4 GB of physical

memory It can support total virtual memory space almost 64 terra byte It is available in 275 K transistors Its operating clock speed is 16 Mhz to 33MhzThis processor has memory management unit with a

segmentation unit and paging unit It operates in Real, Protected and virtual mode Its 80386 instructions set is upward compatible with all its

predecessors80386 processor supports intel 80387 numeric data processor.

Comparison between 80286 and 8038680286 80386 Intel 80286 was developed

in 1983 and it is advanced version of 80186

16 bit processor134K transistor in a 68 pin

IC24 bit address lines , 16

MB of physical memory can be accessed

80286 support numeric processors

8 byte prefetch queue

Intel 80386 was developed in 1985 and it is advanced version of 80286

32 bit processor275K transistor in 132 pin

IC32 bit data and 32 bit

address lines , 4GB of physical address it can support

Supports numeric processors

It is having 16 byte prefetch queue

Features of 80486It has complete 32 bit architectureIt is available in 25 Mhz, 33Mhz, 50Mhz and 100Mhz

clock frequency versionsMore pipe lining has been introduced to improve the

performanceFloating point unit is integrated with 80486 processor

and hence the delay in communication between CPU and FPU has been eliminated

For fast execution of complex instructions, 80486 has 5 stage pipelining 2- decoding and 3 for execution

Clock doubling and clock tripling technology is incorporated in faster versions of intel 80486 cpu

Power management mode is standard feature of 80486

Pentium ProcessorsFeatures

5V processor fabricates in 0.8micron BiCMOS technology

Runs at a clock frequency of 60Mhz/66Mhz and has 3.1 millon transistor

Compatibility with 80386 instructions through a micro programmed CISC unit

It is Super scalar architectureWider 64 bit data buswith pipelined burst mode for

quicker chache line fills and write backsTwo independent integer pipelines and a floating

point pipelineMemory management unit availablePower save function is also available

Block diagram of Pentium architecture

Pentium ProThis is 6th generation processor introduced in

1995It consists of 5.5 million transistorsThis is able to work in dual-processor and quad-

processor configurations.It has 12 stage pipeline architecture36 address bus8KB instruction Cache2 integer units and 1 floating point unitThis are popular in multiprocessing configurationsP6 architure operates in 32 bit OS such as UnixIt operates on 3.1V to 3.3 V