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Agenda: Salient Features of 80386

Functional Block Diagram of 80836

Pin Description of 8086

Register Set of 80386

Flags

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Branch Instruction

Indirect Addressing Diagram

Address AOpcode

Instruction

Memory

Operand

Pointer to operand

Register Addressing DiagramRegister Address ROpcode

Instruction

Registers

Operand

Register Indirect Addressing Diagram

Register Address ROpcode

Instruction

Memory

OperandPointer to Operand

Registers

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°MIPS: “Three-address architecture”•Arithmetic-logic specify all 3 operands

add $s0,$s1,$s2 # s0=s1+s2•Benefit: fewer instructions performance

°x86: “Two-address architecture”•Only 2 operands, so the destination is also one of the sources

add $s1,$s0 # s0=s0+s1•Often true in C statements: c += b;•Benefit: smaller instructions smaller code

Direct Addressing DiagramAddress AOpcode

Instruction

Memory

Operand

Displacement Addressing Diagram

Register ROpcode

Instruction

Memory

OperandDisplacement

Registers

Address A

+

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• In 80386 & above, extended 32-bit register names are: EAX, EBX, ECX, EDX, ESP, EBP, EDI, and ESI.

• 64-bit mode register names are: RAX, RBX, RCX, RDX, RSP, RBP, RDI, RSI, and R8 through R15.

• Important for instructions to use registers that are the same size. – never mix an 8-bit \with a 16-bit register, an 8- or

a 16-bit register with a 32-bit register– this is not allowed by the microprocessor and

results in an error when assembled