Unit 1: Systems Architecture Flashcards
What is the definition of a Computer System?
A computer system is a machine whose job it is to input, process and output data.
What are General Purpose Systems?
General purpose systems is a device (such as smartphones and tablets) that are used for multiple different things.
What is an Embedded System?
Embedded systems are where the computer works as part of a larger system, for example the computer system in a car, or a micro controller in a washing machine. They are only designed to do one specific task, so are often simpler than a general purpose computer.
What does the CPU and Memory do together?
They run programs. In particular, the CPU executes (runs) programs using the fetch-decode-execute cycle, whilst the memory (registers, cache, RAM and virtual memory) store the data amd programs that are currently in use.
What did John Von Neumann do?
He developed a new concept that would allow you to store program instructions as well as data in the memory.
What are the key features of Von Neumann Architecture?
- There is a single memory (and bus system) for accessing both data and programs
- The program stored in main memory and instructions are fetched and executed sequentially.
The way this works is known as the fetch-decode-execute cycle.
What is the Fetch-Decode-Execute cycle?
FETCH - The address of the instruction to be executed is copied from the Program Counter (PC) to the Memory Address
The instruction at that address is fetched from memory and copied to the Memory Data Register (MDR)
DECODE - The Control Unit decodes the instruction and decides if data needs to be fetched
EXECUTE - The instruction is executed
What is the Arithmetic Logic Unit and what does it do?
Arithmetic Logic Unit (ALU) - carries out the arithmetic and logical operations required.
AND, OR , NOT
ADD, SUB etc.
What is CPU performance?
How fast a computer can run depending on a number of factors.
What is Clock Speed?
This determines how many instruction cycles a processor is able to process every second. A clock speed of 2 gHz (gigahertz) for example would mean that 2 billion instruction cycles are processed every second.
The higher the clock speed, the more instructions can be processed every second. However, more instructions processed means more heat, and more power consumed, somall processors have a maximum ‘safe’ clock speed. This can be manually overridden which is known as overclocking.
How does the Number of processor cores affect CPU performance?
A CPU often will contain a number of processing units known as cores, each one consisting of an ALU and a Control Unit, as well as very temporary memory known as registers. The number of cores a processor has determines how many instructions it can process at the same time.
How does Cache size and type affect CPU performance?
Next to the CPU is a very fast (and expensive) type of memory called cache memory. This is where instructions that the computer is likely to reuse are stored. Since constantly fetching instructions from RAM can be slow, the CPU checks the cache memory for instructions before checking RAM, to help speed up the process. This means that the more cache there is, the more of these quick reference instructions can be stored, and therefore the faster the computer can run.
What is the Control Unit and what does it do?
Control Unit (CU) - The control unit coordinates and controls all of the activities taking place within the CPU
- It decodes instructions and executes them
- It receives signals from the system clock
- It directs the timing and control other parts of the CPU
- It decides if data needs to be fetched
What is the clock and what does it do?
Clock - a signal which is used to synchronise everything inside a computer.
What is the Bus and what does it do?
Bus - a collection of wires through which data is transmitted from one component to another.
