Topic 2

Clockspeed

The number of cycles a CPU performs per second. Measured in GHz

Cores

Physical processing units of CPU. Responsible for executing instructions and performing calculations.

Threads

Sequence of instructions given to CPU, allow multitasking.

Control unit

• Controls and coordinates the operations of the computer

• Controls which instructions are done and when

• Direct flow of data between CPU and other devices

Program counter

Stores the memory address of the next instruction to be executed

Memory adress register

Stores the memory address of the current intruction or data that has to be fetched or the data that has to be written to the memory.

Memory data register

It temporarily stores the instruction/data fetched from the memory or data that needs to be written to the memory.

Current instruction register

Holds the current instruction being executed

Accumulator

Stores temporarily the result of the calculations performed by the ALU.

Arithemtic and logic unit

A part of the CPU that performs all of the arithemtic calculations and boolean operations.

Address bus

Physical connection that carries the address of the data from the MAR to the memory.

Data bus

Physical connection that carries data between the MDR and memory.

Control bus

Physical connection that carries control commands from CPU to control and coordinate the activities within a computer.

Primary memory

Memory that the computer can access directly

Random access memory

• Volatile primary storage, so when the power is off the data is lost.

• Stores the current instructions and data

• Holds operating system or any open documents and programs that are running

• It can be read and written to

Issues with small RAM

• Slow performance (vRAM)

• Freezing or crashing

• Inability to run certain programs

• Reduced multi tasking capability

Read only memory

• Non volatile primary storage that keeps the content when the computer is turned off

• Contains the instructions to start the computer

• Can be read but not written to, making it it ideal to store instructions needed for the computer to run.

Cache

• Small, high speed memory found between the CPU and RAM.

• Stores copies of data that have been recently and often used by the CPU.

Role of registers

• Store addresses

• Store instructions

• Store data

• Perform arithmetic operations

Secondary memory

• Non volatile

• Not immediately accessible by the CPU

• It stores program and data

• High storage capacity

Virtual memory

• Often reffered to as ‘cloud storage‘

• Stores and retrievs data over the internet in a cloud rather than locally on a device

Advantages of virtual memory

• Data can be accessed at any time from any device as long as there’s internet connection.

• Data can be easily shared without the need of removable media.

• Easier to collaborate

Disadvantages of virtual memory

• Can be expensive

• With poor internet connection access time is slow

• No internet means no accessing data

Machine instruction cycle

1. Fetch instruction:

2. Decode instruction

3. Execute instruction

4. Store result

AND gate

OR gate

NOT gate

NAND gate

NOR gate

XOR gate