COMPARITVE STUDY OF 80286, 80386, 80486 &PENTIUM PROCESSORS:-

80286 80386 80486 PENTIUM

Specifications16 Bit Processor32 Bit Processor32 Bit Processor32 Bit Processor

No. Of Pins68 132168296

TechnologyHMOSHMOS-3PGA(Pin Grid Array)SPGA(Special Pin Grid Array)

Address Bus24 Bits32 Bits32 Bits32 Bits

Data Bus16 Bits32 Bits32 Bits64 Bits

Memory CapacityPhysical Memory-16MBPhysical Memory-4GBPhysical Memory-4GBOn the whole 4GB

Cache Memory -1GBVirtual Memory -64TBVirtual Memory -64TB

Clock Frequency4,6,8 MHz12.5,16,20,25,33 MHz25,33,50,60&100 MHz60-233 MHz

Addressing Modes8 111111

Functional UnitsBus Unit, Execution Unit,Bus Unit, Pre-fetch Unit,Bus Unit, Pre-fetch Unit,Bus Unit, Paging Unit,

Address Unit, Instruction UnitDecode Unit, Paging Unit,Cache Unit, Floating PointPre-fetch Buffer, Instruction

Segmentation Unit, ExecutionUnit, Decode Unit, ControlDecoder, Control ROM,

UnitUnit, Protection Test Unit,Integer Pipelines(U & V

ALU, Paging Unit,Pipelines), Floating Point

Segmentation UnitUnit, BTB(Branch Target

Buffer), Code Cache & Data

Cache, Dual Processing Logic

and APIC(Advanced

Programmable Interrupt

Controller)

Data Types8,16 Bit- Signed & Unsigned,8,16,32 Bit- Signed &8,16,32 Bit- Signed &8,16,32 Bit- Signed &

SupportedBCD, Strings, ASCII, RealUnsigned, BCD, Strings, 32 &Unsigned, Real Strings, BCD,Unsigned, Real Strings, BCD,

48 Bit-Memory Pointers, BitBit Field, Bit Strings, 32 & 48Bit Field, Bit Strings, 32 & 48

Field, Bit StringsBit-Memory PointersBit-Memory Pointers

Modes OfReal, Protected & VirtualReal, Protected & VirtualReal, Protected & VirtualReal, Protected & Virtual

OperationAddressing ModesAddressing ModesAddressing ModesAddressing Modes

Barrel ShifterAbsentPresent & is 64 BitsPresentPresent

PagingNoYesYesYes

802868038680486PENTIUM

MemoryYesYesYesYes

Management

Protection

RegistersAX, BX, CX, DX, SI, DI, BP,SP,EAX,EBX,ECX,EDX, ESI, EDI,Same As 286 & AdditionalSame As 486 & Additional

DS, ES, SS,CS, IP, Flags, GDTR,EBP,ESP,FS, GS, DS, ES, SS,CS,Registers are TR3,TR4,TR5,Registers are CR0-CR4

LDTR, IDTR, MSWIP, E Flags, GDTR, LDTR, IDTR,Cache Registers

CR0-CR3, TR1, TR2, DR0-DR7

Task SwitchingYesYes, Done by a SpecialYes, Done by a SpecialYes, Done by a Special

HardwareHardwareHardware

Suitable8028780387External Co-Processor,Same

Co-processorsBuilt-in Co-Processor Exist

FlagsCF,PF,AF,SF,ZF,TF,DF,IF,OF,NTCF,PF,AF,SF,ZF,TF,DF,IF,OF,RF,Same As 386 & AuxiliarySame As 486 & ID

& IOPLVM, NT & IOPL(2 Bits)CarryFlag(Identification Flag),

VIP(Virtual Interrupt

Pending), VIF(Virtual

Interrupt)

PipeliningInstruction Fetch, Decode &Instruction Fetch, Decode ,Op-code Fetch, Decode ,U&V Pipeline for Integers

Execution in ParallelExecution, MemoryExecution, Memory1.Pre-fetch

Management & Bus Access inManagement , Bus Access&2.Decode 1

ParallelFloating Point Operation in3.Decode 2

Parallel4.Data Access from

ALU

5.Write Result

Floating Point

1.Pre-fetch

2.Decode 1&2

3.Operand Fetch

4.First Execute

5.Second Execute

6.Write the Result

.

Multiplexing OfNot MultiplexedNot MultiplexedNot MultiplexedNot Multiplexed

Buses

Special FeaturesNothingNothingBIST(Built-In Self Test) & 641.Power Management

Bit Internal Registers2.AP Check(Address

Parity Check)

3.PC Check(Parity

Check Over Data)

4.STPCLK- Stop Clock