1.1 Systems Architecture Flashcards
What is a computer? What is its purpose?
A computer is a machine that processes data
Its purpose is to take data, process it, then output it (A.K.A FDE cycle)
What does a computer consist of?
Hardware and software that work together to process data / complete tasks
What is hardware?
The physical components of a computer
Give 3 examples of hardware in a computer system
CPU, RAM, ROM, motherboard, HDD, SSD, CPU heatsink and cooling fan, power supply, optical drive, graphics card
What is software?
Programs or applications that a computer system runs
Give 3 examples of software
OS, word processor, videogame, web browser, graphics software
What are peripherals?
External pieces of hardware e.g. keyboard, mouse, printer
What are the two types of computer systems and what are they used for?
General purpose systems are designed to perform many tasks e.g. PC, tablet, mobile phone
Embedded systems are designed for one particular function and are computers built into other devices e.g. dishwasher, digital camera, robotic vaccum cleaner, microwave, TV
What is the function of the CPU?
To process all of the data and instructions that make the computer system work
It is the ‘brain’ of the computer system
What is the Fetch-Decode-Execute cycle?
The method a computer uses to carry out instructions
What occurs in the fetch stage of the F-D-E cycle?
1) The memory address of the next instruction to be executed is copied from the Program Counter to the MAR
2) The instruction stored in the memory address in the MAR is copied to the MDR
3) The PC is incremented by one so it is ready for the next F-D-E cycle
What occurs in the decode stage of the F-D-E cycle?
The instruction in the MDR is decoded by the Control Unit and it coordinates a response
What occurs in the execute stage of the F-D-E cycle?
The instruction is executed
e.g. load data from memory, write data to memory, do a calculation or logic operation, halt the program
F-D-E cycle in full
1) The memory address of the next instruction to be executed is copied from the Program Counter to the MAR
2) The instruction stored in the memory address in the MAR is copied to the MDR
3) The PC is incremented by one so it is ready for the next F-D-E cycle
4) The instruction in the MDR is decoded by the Control Unit and it coordinates a response
5) The instruction is executed
What are the 4 main components of the CPU?
Control Unit (CU)
Arithmetic Logic Unit (ALU)
Cache
Registers
What is the function of the CU?
1) Manages the fetching, decoding and executing of instructions (F-D-E cycle)
2) Controls the flow of data inside the CPU (to ALU, registers etc.) and outside the CPU (to memory and input/output devices)
What is the function of the ALU?
1) Performs mathematical calculations
2) Performs logic operations (AND, OR, NOT) and binary shifts
What is the function of the cache?
1) Stores frequently used data and instructions so the computer can access it quickly
What are some characteristics of the cache?
1) The cache is very fast memory in the CPU (faster than RAM but slower than registers)
2) Caches have a very low capacity and are very expensive per MB compared to RAM and secondary storage
3) There are different levels of cache memory. L1 is the fastest but has the lowest capacity. L3 is the slowest but has the highest capacity. L2 is in the middle
What is the general function of registers?
Temproarily hold tiny bits of data needed by the CPU
What is the main benefit of registers?
They are super quick to read/write to (much faster than any other form of memory)
What are the 4 registers?
Control Unit (CU)
Memory Address Register (MAR)
Memory Data Register (MDR)
Accumulator
What is the function of the PC?
Stores the memory address of the next instruction to be fetched
What is the function of the MAR?
Stores the memory address of the instruction that is currently in use
What is the function of the MDR?
Stores the contents found at the address stored in the MAR
What is the function of the accumulator?
Stores the results of calculations from the ALU
What are the 3 factors that affect CPU performance?
Clock speed
Number of cores
Cache size
What is a core?
An individual processing unit within the CPU
How does clock speed affect CPU performance?
1) Clock speed determines the number of instructions that each processor core can carry out per second (measured in hertz)
2) The higher the clock speed, the greater the number of instructions that can be carried out per second
What is overclocking and how does it affect CPU performance?
1) Overclocking is when the CPU is made to run at a higher clock speed than the factory-set rate
2) This can increase the number of instructions that can be carried out per second
3) HOWEVER it can make the CPU overheat, which can cause crashes or permanent damage to the system (high performance cooling systems are usually required to overclock successfully)
How does the number of cores affect CPU performance?
1) Each core the a CPU can process data independently. Therefore, the more cores a CPU has, the more instructions it can carry out per second
2) HOWEVER, some applications or programs do not support the use of multiple cores so an increase in the number of cores may not increase performance for these
How does cache size affect CPU performance?
Cache memory is faster than RAM, so a larger cache gives the CPU faster access to more data that it needs to process (as it doesn’t need to be fetched from RAM)
What is an embedded system?
A computer that is built into other devices and designed for one specific purpose
What are the typical characteristics of embedded systems?
Cheaper to design and build (as have limited number of functions)
Require less power (some can be run on batteries)
Do not need much processing power so built with cheaper, less powerful processors
Give 3 examples of embedded systems
Central heating devices
Dishwasher
TV
Digital watch
Electronic calculator
GPS system
Fitness tracker
Engine management system in a vehicle
