Basic Operational Concepts in Computer Architecture

Basic Operational Concepts

• The Add R4, R2, R3 instruction adds the contents of registers R2 and R3 and places their sum into register R4.
• The original contents of R2 and R3 are not altered, but the previous value in R4 is overwritten.
• The Store R4, LOC instruction copies the operand in register R4 to memory location LOC.
• The original contents of location LOC are overwritten, but those of R4 are preserved.
• Load and Store instructions transfer data between the memory and the processor by sending the address of the desired memory location to the memory unit.
• The data is then transferred to or from the memory.

Processor Components

• The processor contains an Arithmetic Logic Unit (ALU), control circuitry, and numerous registers.
• The instruction register (IR) holds the instruction currently being executed.
• The program counter (PC) contains the memory address of the next instruction to be fetched and executed.
• General-purpose registers (R0 through Rn−1) serve various functions, including holding operands from memory for processing.

Memory and Processor Connection

• The processor-memory interface manages the transfer of data between the main memory and the processor.

VLSI Technology

• Very Large Scale Integration (VLSI) technology fabricates processor circuits on a single chip, impacting instruction execution speed.
• Smaller transistors switch faster, leading to faster execution.
• Advances in fabrication technology have significantly reduced transistor sizes, allowing for faster execution and increased logic functionality and memory storage capacity.

Parallelism

• Executing multiple operations in parallel improves performance.
• Instruction-level parallelism: Overlapping the execution of successive instructions reduces total execution time.
• Pipelining: Fetching the next instruction while the current instruction's arithmetic operation is being performed.

Multicore Processors

• Multiple processing units are fabricated on a single chip, referred to as cores.
• Dual-core, quad-core, and octo-core processors have two, four, and eight cores, respectively.

Multiprocessors

• Computer systems with multiple processors, each potentially containing multiple cores, are called multiprocessors.
• These systems can execute multiple application tasks or subtasks of a single task in parallel.
• Multiprocessors typically have shared access to all memory, often called shared-memory multiprocessors.
• Although these systems offer high performance, they are more complex and costly due to multiple processors, memory units, and complex interconnection networks.

Word Alignment

• Word alignment ensures that words begin at a byte address that is a multiple of the number of bytes in a word.
• The common convention is to number bits within a word or byte from left to right, with the most significant bit on the left and the least significant bit on the right (Figure 2.6a).

Instruction Set Architecture:

• Instructions are categorized by their operation types:
  • Data transfers between memory and processor registers
  • Arithmetic and logic operations on data
  • Program sequencing and control
  • I/O transfers

Register Transfer Notation (RTN)

• RTN uses symbolic names for locations and square brackets to denote the contents.
• R1 ← [LOC] means transferring the contents of memory location LOC into processor register R1.
• R3 ← [R1] + [R2] means adding the contents of registers R1 and R2 and placing their sum into register R3.

Assembly Language Notation

• Assembly language uses mnemonic codes (e.g., Load, Add) to represent machine instructions.
• Load R2, LOC transfers data from memory location LOC to processor register R2.
• Add R4, R2, R3 adds the contents of registers R2 and R3 and places the sum in register R4.

Addressing Modes

• Index Mode: Uses a register to provide an offset from a base address to reach the actual operand.
• X(Ri) indicates an offset X from the address in register Ri.
• The effective address (EA) is calculated as: EA = X + [Ri].

Indexed Addressing Example:

• A list of student test scores stored in memory uses Indexed addressing mode.
• Register R2 acts as the index register to navigate through student records.
• By using offsets (e.g., 4(R2), 8(R2), 12(R2)), the program accesses scores within each record.

This quiz explores foundational operational concepts and processor components in computer architecture. It covers key instructions such as addition and storage, detailing how data transfer occurs between registers and memory. Test your understanding of these principles and how they influence processing tasks.