Fundamentals of Computer Organisation and Architecture Flashcards
What is the Processor?
It executes program instructions to run applications.
What is Main Memory?
It includes RAM and ROM to store program instructions and frequently used data.
Main Memory is usually much faster than secondary storage so storing frequently used data in main memory helps execute instructions faster.
What are Buses in a computer?
They are parallel wires connecting internal components, allowing signals to pass between them.
What is the Address Bus?
It transports memory addresses, specifying where data is to be sent or retrieved from.
What is the Data Bus?
It sends data and instructions to and from different components of the computer system.
What is the Control Bus?
It carries control signals that regulate the operation of the computer system and the computer’s clock signal.
What are I/O Controllers?
They control the communication of data between the processor and external hardware devices.
What is the Harvard Architecture?
It uses two separate main memory locations, one for instructions and another for data.
Used in RISC Processors (embedded systems).
Doesn’t use registers.
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What are the advantages of Harvard architecture?
Avoids possibility of data being executed as code, memory mix-up.
Avoid the “Von Neumann” bottlenecks.
CISC
Complex Instruction Set Computer. Offers hundreds of instructions of variable sizes.
RISC
Reduced Instruction Set Computer. Uses a small set of instructions of uniform length.
Key difference between RISC and CISC
RISC uses simple instructions executed in one clock cycle, while CISC offers a large set of complex instructions.
What is the Von Neumann Bottleneck?
The Von Neumann bottleneck is a limitation in computer architecture where the speed and performance of a computer are limited by the rate at which data can be transferred between the computer’s processor and its memory.
In simple terms, it’s like a road with heavy traffic where the speed of cars (data) is limited by the narrowness of the road (data bus).
How does Harvard Architecture avoid the Von Neumann bottleneck?
By having separate storage and buses for instructions and data.
This allows the CPU to fetch instructions AND read/write data simultaneously; increasing speed.
What is the Von Neumann Architecture?
It stores both instructions and data together in the same memory.
What is the Stored Program Concept?
Stored Program Concept: It’s the idea that a computer’s instructions (machine code) are kept in main memory and executed one-by-one by the processor, which performs arithmetic and logical operations. This forms the basis of modern computer design.
What is the Arithmetic Logic Unit (ALU)?
It performs arithmetic and logic operations like addition, AND, OR, and XOR.
It uses general purpose registers to temporarily hold the results of calculations.
What is the Control Unit?
It coordinates all activities of the CPU, directs data between CPU and other devices, accepts and decodes instructions and handles their execution.
Sends read/write requests to main memory on the control bus.
What are General Purpose Registers?
They can be used as storage for any data required by instructions during execution.
Found in the processor.
What is the Program Counter (PC)?
It holds the memory address of the next instruction to be executed in the fetch-execute cycle.
What is the Current Instruction Register (CIR)?
It holds the instruction that is currently being executed by the processor.
What is the Memory Address Register (MAR)?
It stores the memory address of a memory location that is to be read from or written to.
What is the Memory Buffer Register (MBR)?
Also called the memory data register (MDR), it holds the contents of a memory location that has been read from or data that is to be stored.
“Gateway to the processor”
What is the Status Register (SR)?
It contains a number of bits, the values of which can change to indicate the occurrence of an interrupt.
What is the Clock?
It generates a regular electronic pulse to synchronise communication between the components of the processor and the rest of the computer system.
Fetch:
Transfer PC to MAR
use address bus to transfer address to main memory
transfer contents of addressed memory location to MBR
increment PC
copy MBR to CIR.
Decode:
Decode instruction held in CIR
control unit decodes instruction
split instruction into opcode and operand.
Execute:
If necessary, fetch data
if necessary, store data in memory
perform operation identified by opcode using ALU
store result in register or accumulator
update status register
if jump or branch required, update PC.
During the decode and execute stages the instruction being processed is stored in the CIR. Explain why the instruction could not be processed directly from the MBR
To carry out the instruction other data may need to be fetched from main memory
Further memory fetches would overwrite the contents of the MBR
What is a processor’s instruction set?
The group of instructions that a processor can carry out. Each type of processor has its own instruction set.
How are instructions usually stored in a processor?
Instructions are usually stored in machine code.
What are the two primary parts of an instruction?
Opcode and one or more operands.
What does the opcode specify?
The type of operation that is to be carried out, for example: addition, subtraction or logical shifting.
What are operands?
The pieces of data on which the operation is performed.
What is an addressing mode?
Bits in a machine code instruction is usually assigned to the addressing mode in use.
