Computer Architecture Quiz

Instruction Cycles

• The fetch-execute cycle, in the Little Man Computer, is divided into two phases: fetch and execute.
• The fetch phase is the same for every instruction because it involves retrieving the instruction from memory and placing it in the Instruction Register.
• The fetch-execute cycle is the basic process by which a computer executes instructions.

Von Neumann Architecture

• A von Neumann architecture is characterized by the following features:
  • Single address space for both instructions and data: All instructions and data are stored in the same memory location.
  • Sequential processing of instructions: Instructions are executed one after another in a linear fashion.
• The execution of an addition operation in the Little Man Computer illustrates these criteria by demonstrating how an instruction and the data it operates on are both stored in the mailbox locations of the Little Man computer's model.
• The instruction to add two numbers and the numbers themselves are stored in the memory before are fetched by the Little Man and processed.
• The fetched instructions are also processed in a linear fashion- one after the other.

Memory Types

• Volatile memory loses its data when the power is turned off. RAM is volatile.
• Nonvolatile memory retains its data even when the power is turned off. ROM is nonvolatile.

Registers, Fetch-Execute, And The Little Man

• Registers play an important role in the fetch-execute cycle by temporarily storing data that is being processed.
• The fetch part of the fetch-execute cycle involves the following steps:
  • Fetch: The Program Counter (PC) contains the address of the next instruction to be fetched.
  • The PC is copied to the Memory Address Register (MAR).
  • The Memory Data Register (MDR) receives the instruction based on the address stored in the MAR.
  • The contents of MDR are transferred to the Instruction Register (IR).
• The fetch operation prepares the instruction for execution by retrieving it from memory and placing it in the IR.
• The Little Man retrieves instructions from his mailboxes and processes them in a similar way to a computer.
• The Little Man represents the CPU, the mailboxes represent the memory, and the instructions are the information he retrieves from the mailboxes.

Bus

• A bus is the physical connection for data transfer between different components of a computer system. This includes
  • transfer of data between memory and the CPU
  • transfer of data between the CPU and I/O devices
• It is a group of electrical or optical conductors.
• There are four kinds of signals:
  • Data
  • Addressing
  • Control signals
  • Power signals
• Bus characteristics:
  • The number of conductors determines how much data can be transferred simultaneously (data width).
  • The Addressing capacity refers to the number of memory locations that can be accessed.
  • Throughput is the rate at which data can be transferred.

Types of Buses

• Parallel buses transfer all bits of a word simultaneously.
  • They have high throughput but are expensive.
  • Parallel buses are used in CPU buses and computer motherboards.
• Serial buses transfer one bit at a time.
  • They are less expensive and can be used over longer distances but have lower throughput.
  • Serial buses are used for peripherals and networking.
• Point-to-point buses connect single sources to single destinations.
  • Example: Devices connected to a computer via cables.
• Multipoint buses (also broadcast bus or multidrop bus) connect multiple points to one another.
  • Example: Ethernet.

Instruction Classifications

• Data Movement (load, store):
  • Most common instructions.
  • Involve memory and registers.
  • This involves transferring data between memory and registers.
• Arithmetic:
  • Performs arithmetic operations such as addition, subtraction, multiplication, division, and exponentiation.
• Boolean Logic:
  • Performs logical operations such as AND, OR, XOR, and NOT. This is used for decision-making and conditional execution of instructions.
• Single Operand Manipulation instructions:
  • Operate on a single operand, such as negating, decrementing, incrementing, or setting to 0. This kind of instruction changes the value of a single data item.
• Bit manipulation instructions:
  • Operate on individual bits within a word or byte.
  • This can be used for efficiently controlling the individual bits of data.
• Shift and rotate instructions:
  • Shift or rotate the bits of a data word. This changes the bit pattern of data by shifting it to the left or right or rotating it cyclically.
• Program control instructions:
  • Control the flow of execution, such as jumps, branches, subroutines calls and returns. This allows for the execution to skip to a new instruction.
• Stack instructions:
  • Manage data on stack. Stack instructions enable the use of a stack data structure for managing temporary data, such as function arguments and local variables.
  • Stack operations include push and pop.
• Multiple data instructions:
  • Perform a single operation on multiple pieces of data simultaneously.
  • SIMD (Single Instruction, Multiple Data) is commonly used in multimedia, vector, and array processing applications.
• Input/Output (I/O) and machine control instructions:
  • Interact with the computer's hardware, such as I/O devices, timers, and interrupts. This allows for data interaction with external devices.

Instruction Format

• The instruction format is defined in a template that specifies:
  • Length of the op code (the part of the instruction that identifies the operation to be performed by the processor)
  • Number of operands
  • Length of operands
• Instruction set:
  • A set of instructions that a particular processor can execute.
  • The instruction set defines the functions performed by the processor, differentiating it from other computer architectures.

Instruction Word Size

• Fixed instruction word size allows for efficient pipelining.
• Variable instruction word size is generally not used in modern architectures because it presents challenges for pipelining and performance.
• Common word sizes include 32 and 64 bits.

Addressing Modes

• Direct addressing: Mode used by the LMC
• Register deferred addressing:
• Immediate addressing:
• Indirect addressing:
• Indexed addressing:
• Addressing modes tell the processor how to find the data that an instruction operates on.

Test your knowledge on instruction cycles and von Neumann architecture with this quiz. Explore concepts like the fetch-execute cycle and the characteristics of a computer's architecture. Perfect for students studying computer science.