Chapter 1: Basic Organization of Von Neumann Computer

Who formalized the Von Neumann architecture and when?

John von Neumann, in 1945, with the IAS computer at Princeton.

What is the Von Neumann architecture?

It is a stored program concept where instructions and data are both stored in RAM and executed sequentially by the CPU.

What are the main components of a Von Neumann computer system?

CPU, memory, and I/O devices, all connected by a bus.

What are the key features of Von Neumann architecture?

• Stored program concept (one machine runs many programs).

• CPU and RAM are separate.

• Instructions and data fetched from RAM.

• Results stored in registers then written back to memory.

What are the three main types of buses in a computer system?

Control Bus, Data Bus, and Address Bus.

What is the function of the control bus?

Carries control and coordination signals (read, write, reset) across the computer.

What is the function of the data bus?

Bi-directional exchange of data between processor, memory, and peripherals.

What is the function of the address bus?

Carries memory addresses from CPU to memory; its width determines maximum addressable memory locations (2^N).

What is memory in a computer system?

A collection of numbered cells (bits/bytes) used to store instructions and data.

What is address space?

The total number of unique memory addresses a system can use, determined by address width (2^N).

What are the two key operations on memory?

• Fetch(address): Reads data from a memory location.

• Store(address, value): Writes data to a memory location.

Which registers are used in memory operations?

• MAR (Memory Address Register) – stores address.

• MDR (Memory Data Register) – stores data being transferred.

What is cache memory and why is it used?

A small, fast memory that stores frequently used data to reduce fetch/store delays compared to slower main memory.

What are common memory size measurements?

1 Byte = 8 bits, 1 KB = 1024 Bytes, 1 MB = 1024 KB, up to Yottabytes (YB), Brontobytes, and Geopbytes.

What are registers and why are they important?

Small, high-speed storage inside CPU for quick data access; faster than memory but expensive.

What are the types of registers in Intel 8086 CPUs?

• 32-bit: EAX, EBX, ECX, EDX, ESI, EDI, EBP, ESP.

• 16-bit: AX, BX, CX, DX, SI, DI, BP, SP. 

• 8-bit: AL, AH, BL, BH, CL, CH, DL, DH.

What is the Arithmetic Logic Unit (ALU)?

The CPU component responsible for arithmetic (add, subtract) and logic operations (AND, OR, NOT, XOR).

What are the basic operations of the ALU?

Logical operations, bit-shifting, and arithmetic operations (addition, subtraction, multiplication via addition, division via subtraction).

What is the role of the decoder in CU?

Interprets instructions (based on opcode and addressing mode) to determine necessary actions.

What is the role of the timer/clock in CPU?

Synchronizes CPU operations with regular pulses.

What is the role of control logic circuits in CU?

Generate control signals that instruct ALU and registers on what actions to perform.

What is the Fetch-Decode-Execute cycle?

The basic process of CPU operation: fetch instruction, decode it, then execute it.

How is processor speed measured?

In Hertz (Hz), representing cycles per second (e.g., 3.8 GHz = 3.8 billion cycles/sec).

What is the role of the Input/Output unit?

Manages communication with external devices (disks, printers, keyboards, displays, etc.) via the I/O controller, often using interrupts.