Intel 8086 Microprocessor Architecture

Questions and Answers

What is the maximum amount of memory that the Intel 8086 microprocessor can access?

1 MB (correct)

512 KB

256 KB

2 MB

Which component of the Intel 8086 microprocessor handles the actual execution of instructions?

Instruction queue

Bus Interface Unit (BIU)

Address adder

Execution Unit (EU) (correct)

In which operational modes can the Intel 8086 microprocessor function?

Basic and Advanced

Single and Dual

Minimum and Maximum (correct)

Standard and Custom

What is the word size of the Intel 8086 microprocessor?

16 bits Signup and view all the answers

What is the purpose of the Instruction Queue in the Intel 8086's Bus Interface Unit?

To prefetch instructions and speed up execution Signup and view all the answers

What is the purpose of the AX register in the execution unit?

Used for word multiply, word divide, and word I/O Signup and view all the answers

Which register is primarily used to access data on the stack?

SP Signup and view all the answers

What is the role of the SI register during string operations?

It points to memory locations in the data segment. Signup and view all the answers

What does the DX register specifically handle during I/O operations?

It holds both higher and lower order results during I/O. Signup and view all the answers

Which of the following registers is typically used with the Data Segment register (DS)?

SI Signup and view all the answers

In the context of memory addressing, what do the pointer and index registers primarily store?

Offset addresses for memory addressing. Signup and view all the answers

What is the main function of the BX register?

To hold address information. Signup and view all the answers

Which register is not primarily associated with arithmetic functions?

SP Signup and view all the answers

What is the primary purpose of the Destination Index (DI) register in string operations?

To point to memory locations in the data segment. Signup and view all the answers

Which flags in the flag register indicate conditions in the execution unit?

Overflow, Sign, Parity Signup and view all the answers

What does the Carry Flag (CF) indicate after an addition or subtraction operation?

The carry after addition or borrow after subtraction. Signup and view all the answers

How many active flags are there in the 16-bit flag register of the 8086 execution unit?

9 Signup and view all the answers

What is the function of the Zero Flag (ZF)?

Shows the result of an arithmetic or logic operation. Signup and view all the answers

What does the Direction Flag (DF) select during string instructions?

The increment or decrement mode for DI and/or SI. Signup and view all the answers

Which of the following flags is used to control the operation of the INTR pin?

Interrupt Flag (IF) Signup and view all the answers

What kind of information does the Auxiliary Flag (AF) hold after an addition operation?

The carry between bit positions 3 and 4. Signup and view all the answers

What is indicated by an overflow when adding signed numbers?

The result is too large to be represented. Signup and view all the answers

Which flag indicates that the sign bit has changed during an arithmetic operation?

Overflow Flag (OF) Signup and view all the answers

How many bytes can the instruction queue in the Bus Interface Unit (BIU) hold?

6 bytes Signup and view all the answers

What is the primary function of the code segment in segmented memory?

Storing the executable instructions. Signup and view all the answers

What happens when the instruction queue of the BIU is not full?

It can pre-fetch the next instruction. Signup and view all the answers

What is the size of each segment in an 8086/88 based system?

64 KB Signup and view all the answers

Which segment is specifically used for storing return addresses?

Stack Segment Signup and view all the answers

What is the total amount of physical memory that the CPU 8086 can address?

1 MB Signup and view all the answers

What is the purpose of the segment registers in the 8086/88 processors?

To store the upper 16 bit address of the starting address of segments. Signup and view all the answers

How does the CS:IP mechanism work in address formation?

CS is left-shifted and added to IP to determine the next address. Signup and view all the answers

Which of the following segments has a specific register designated for stack operations?

Stack Segment register (SS) Signup and view all the answers

What is the size of each segment in the 8086/88 memory model?

64k bytes Signup and view all the answers

In which configuration is the Extra Segment register (ES) primarily used?

For string operations Signup and view all the answers

What is the output of the following combination: CS = 34BA and IP = 8AB4?

$3D654$ Signup and view all the answers

Which segment register is used in conjunction with the Base Pointer (BP)?

Stack Segment (SS) Signup and view all the answers

What does the acronym BIU stand for in the context of the 8086 microprocessor?

Bus Interface Unit Signup and view all the answers

Study Notes

Features of Intel 8086 Microprocessor

16-bit microprocessor with a 20-bit address bus, capable of addressing 1 MB of memory.
Supports up to 64K I/O ports and has a word size of 16 bits, double word size of 4 bytes.
Uses multiplexed address/data bus (AD0-AD15 and A16-A19).
Operates in two modes: Minimum and Maximum.
Can prefetch up to 6 instruction bytes from memory, queuing them for faster execution.
Requires +5V power supply and comes in a 40-pin dual in-line package.

Internal Architecture of 8086

Comprises two main blocks: Bus Interface Unit (BIU) and Execution Unit (EU).
BIU is responsible for data and address transactions, instruction fetching, and operand memory access.
Instruction bytes are transferred to an instruction queue for the EU, which executes the fetched instructions.

Execution Unit Components

Decodes instructions fetched by the BIU, generates control signals, and executes them.
Key components include Control Circuitry, Instruction Decoder, and Arithmetic Logic Unit (ALU).

General Purpose Registers

AX, BX, CX, and DX registers are 16 bits, split into lower (AL, BL, CL, DL) and upper halves (AH, BH, CH, DH).
Registers are used for various arithmetic, I/O, and data storage functions.

Pointer and Index Registers

SP (Stack Pointer) and BP (Base Pointer) are used with the Stack Segment (SS) for managing stack operations.
SI (Source Index) and DI (Destination Index) are utilized in string operations, often associated with the Data Segment (DS) and Extra Segment (ES).

Flag Register

Contains 16 bits, with 9 active flags; reflects conditions from instruction execution and controls EU operations.
Status flags include Carry (CF), Parity (PF), Auxiliary (AF), Zero (ZF), Sign (SF), and Overflow (OF).
Control flags include Trap (TF), Interrupt (IF), and Direction (DF).

Instruction Queue and Pipelining

BIU features a 6-byte instruction queue allowing pre-fetching of instruction bytes, facilitating a pipelining architecture.
When the queue has space, it can look ahead to retrieve upcoming instructions.

Segmented Memory Organization

Memory is logically segmented into four 64KB segments: Code, Data, Extra, and Stack.
Each segment serves specific functions, with addresses generated by segment registers.

Segment Registers

Four segment registers: Code Segment (CS), Data Segment (DS), Extra Segment (ES), and Stack Segment (SS) all store upper 16 bits of segment addresses.

Memory Address Generation

Physical addresses are generated using segment registers and offset values, combining 20 bits of address space.
Example CS:IP address formation illustrates the process of address generation using hexadecimal shifting.

Summary of Registers and BIU Interaction

Registers include AX, BX, CX, DX, SP, BP, SI, DI, with the BIU managing instruction fetching and execution.
The execution is coordinated through a pipeline potentially leveraging both the EU and BIU for efficient processing of commands.

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Description

Explore the functionalities and features of the Intel 8086 microprocessor in this quiz. Learn about its architecture, modes of operation, and memory access capabilities. Test your knowledge on this foundational component of computer engineering.