7. Systems architecture Flashcards
Arithmetic Logic Unit (ALU)
Function: Performs arithmetic operations (addition, subtraction, multiplication, division) and logical operations (AND, OR, NOT) on data.
Example: Calculates expressions like X + Y or X > 5.
Control Unit (CU)
Function: Coordinates data movement within the CPU by sending control signals. Decodes instructions fetched from memory to direct operations.
Example: Sends signals to fetch data from memory and instructs ALU on which operation to perform.
Clock
Function: Generates regular electronic pulses to synchronize operations within the CPU. Ensures that all parts of the CPU operate at the same pace.
Example: Maintains a constant rhythm (e.g., 1 GHz) for processing instructions.
Registers
Function: Fast, small storage locations within the CPU used to hold temporary data and instructions during processing.
Types:
- Accumulator (ACC): Stores results of arithmetic and logical operations.
- Memory Address Register (MAR): Holds the memory address of data or instructions being accessed.
- Memory Data Register (MDR): Stores data fetched from or to be written to memory.
- Program Counter (PC): Keeps track of the memory address of the next instruction to be executed.
Bus
Function: Collection of wires or pathways that transmit signals and data between different components of the computer system.
Example: Transfers data between the CPU and memory (via MAR and MDR) or between CPU components like ALU and registers.
Clock speed
- The clock speed is measured in Hertz (Hz)
- The clock speed measures the number of fetch-decode-execute cycles that can take place in 1 second
- The faster the clock speed, the more instructions can be fetched and executed per second
- Modern computers have a clock speed in Gigahertz (GHz), meaning billion
- A clock speed of 3.5GHz can perform up to 3.5 billion instructions per second
Cache size
- Cache is very small, very fast memory on or close to the CPU
- Cache is used as temporary storage to provide quick access to a copy of frequently used instructions and data
- The larger the cache size, the more frequently used instructions or data can be stored
- This results in the CPU having to complete fewer fetch cycles from memory (RAM), speeding up the performance
Cache also has a significantly faster read/write speed than RAM, making it much quicker to retrieve instructions from there instead of from memory (RAM)
Processor cores
- A processor core works like it is its own CPU
- Multiple core processors mean they have multiple separate processing units that can fetch, decode and execute instructions at the same time
- Multi-core processors can run more powerful programs with greater ease
- Multiple cores increase the performance of the CPU by working with the clock speed
What is the purpose of the CPU?
- The purpose of the Central Processing Unit (CPU) is to fetch, decode and execute instructions
- The CPU is the brain of the computer and its job is to take an input, process data and produce an output
Fetch stage
- During the fetch stage of the cycle, the next instruction or data must be fetched from the computer’s memory (RAM)
- The instruction or data is brought back to the CPU
Decode stage
- During the decode stage of the cycle, the CPU needs to work out what is required from the instruction
- This could be a range of tasks depending on what the instruction or data included
Execute stage
- During the execute stage of the cycle, the CPU will carry out the instruction that was fetched
- Some examples that would take place at this stage are
Performing a calculation
Storing a result or data back in main memory (RAM)
Going to main memory to fetch data from a different location
Embedded
An embedded system is a computer system with a dedicated function, inside a larger mechanical unit
Non-embedded system
A non-embedded system is a computer system with multiple functions, referred to a general-purpose machine
An embedded system compared to a non-embedded system
embedded system is typically:
smaller in size
lower power
lower cost
lower processing power
lower memory
Examples of embedded systems
Heating thermostats
Hospital equipment
Washing machines
Dishwashers
Coffee machines
Satellite navigation systems
Factory Equipment
Traffic lights
