Concept Notes: 8086 Microprocessor Architecture
🔹 1. Introduction to 8086
- The Intel 8086 is a 16-bit microprocessor introduced by Intel in 1978.
- It has a 20-bit address bus → can access 1 MB memory.
🔹 2. Key Features of 8086
- 16-bit ALU
- 20-bit address bus, 16-bit data bus
- Segmented memory architecture (Code, Data, Stack, Extra)
- Clock speeds: 5 MHz to 10 MHz
🔹 3. Major Functional Units
| Unit | Function |
|---|---|
| EU (Execution Unit) | Executes instructions, handles ALU and registers |
| BIU (Bus Interface) | Interacts with memory and I/O, manages instruction queue |
🔹 4. Important Registers
| Register Type | Examples | Purpose |
|---|---|---|
| General | AX, BX, CX, DX | Multipurpose registers |
| Segment | CS, DS, SS, ES | Access different memory areas |
| Pointer/Index | SP, BP, SI, DI | For stack & memory operations |
| IP | Instruction Pointer | Points to next instruction |
| FLAGS | Status register | Shows result of operations |
🔹 5. Memory Segmentation
- Memory is divided into 4 segments:
- Code Segment (CS)
- Data Segment (DS)
- Stack Segment (SS)
- Extra Segment (ES)
Each segment is of 64 KB.
🔹 6. Instruction Queue
- Prefetch queue of 6 bytes in BIU → increases execution speed by pipelining.
🧠 MCQs – 8086 Microprocessor
1️⃣ How many bits is the Intel 8086 processor?
A) 8-bit
B) 16-bit
C) 32-bit
D) 64-bit
2️⃣ What is the maximum memory 8086 can address?
A) 64 KB
B) 128 KB
C) 1 MB
D) 2 MB
3️⃣ Which unit executes the instructions in 8086?
A) Memory Unit
B) Register Unit
C) Execution Unit (EU)
D) ALU only
4️⃣ Which register stores the address of next instruction?
A) SP
B) IP
C) SI
D) CS
5️⃣ How many general-purpose registers are in 8086?
A) 2
B) 4
C) 8
D) 16
6️⃣ What is the size of instruction queue in 8086?
A) 2 bytes
B) 4 bytes
C) 6 bytes
D) 8 bytes
7️⃣ Which of the following is not a segment register?
A) CS
B) DS
C) AX
D) SS
8️⃣ Which register is used as stack pointer?
A) BP
B) SP
C) SI
D) DX
9️⃣ The segment size in 8086 is:
A) 32 KB
B) 64 KB
C) 1 MB
D) 256 KB
🔟 What is the main function of BIU?
A) Executes instructions
B) Performs arithmetic
C) Manages memory & IO operations
D) Controls flags
✅ Answer Key
| Q.No | Answer |
|---|---|
| 1 | B |
| 2 | C |
| 3 | C |
| 4 | B |
| 5 | C |
| 6 | C |
| 7 | C |
| 8 | B |
| 9 | B |
| 10 | C |
🧠 Explanations
- Q1: 8086 is a 16-bit processor.
- Q2: With 20-bit addressing, it accesses up to 1 MB.
- Q3: EU executes instructions.
- Q4: IP → Instruction Pointer.
- Q5: AX, BX, CX, DX, and their halves → total 8 general-purpose.
- Q6: Queue has 6-byte capacity.
- Q7: AX is a general-purpose register.
- Q8: SP = Stack Pointer.
- Q9: Segment size is 64 KB.
- Q10: BIU = memory/data bus handler.
📥 PDF Download
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