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System Architecture: CPU (Components of the CPU (Registers: Memory…
System Architecture: CPU
Components of the CPU
Arithmetic Logic Unit: Performs arithmetic and logical operations to carry out program instructions.
The ALU carries out activities such as : subtraction, addition. multiplication and division aswell as comparisons between two different numbers.
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Clock: Controls the rate at which program instructions are carried out, by sending control electrical signals at regular intervals, called cycles.
Clock Speed: The CPU carries out one program instruction for each clock cycle. Clock speed is usually measured in gigahertz (GHz). 1 GHz is 10*9 cycles per second. Mst home computers have clock speeds between 1 and 3 GHz.
The clock speed is one significant factor that affects performance of the CPU. Other factors include cache size, the number of cores and type of RAM, and hard drive speed.
Buses: Electrical conductors that carry electrical signals between components in the CPU and the other components on the motherboard.
Fetch-Decode-Execute
Fetch
The CPU fetches some data and instructions from Main
Memory and store them in it's own temporary memory called registers. For them to switch you need to use an hardware piece
called the 'address bus' so the address of the next item that the CPU wants will be placed on the address bus. Then the data from the RAM travels top the CPU by another piece of hardware called 'data bus'.
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Performance of the CPU
Clock Speed": The clock is a vibrating quartz crystal and the faster it vibrates, the faster the instructions are processed - at least 1 per cycle. Rates of 3GHz are common in modern computers.
The processor generates a lot of heat and the amount increases with the rate at which it processes instructions. The faster the clock speed, the hotter it gets, which causes it to malfunction and therefore it cannot be increased indefinitely.
The processor must have a heat sink and a fan to dissipate this heat. Liquid nitrogen is needed to cool suoercomputers with clock speeds of 9GHz.
Cache Memory: Cache memory is very fast memory, usually within the processor itself.
The cache speeds up processing by storing recently or frequently used instructions so that they do not have to be fetched from the main memory which is much slower.
As the cache becomes larger it takes longer to find the data and so it becomes slower. Therefore, it is split into different levels, e.g L1, L2 with the smallest nearest to the CPU.
Multi-Core Processors: A multi-core processor contains more than one CPU. Multi-core processors can give faster processing speeds than single-core processors and can work on different tasks at the same time.
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Embedded Systems
Components in Embedded Systems: are on printed circuit board (PCB). They include the: processor, memory, input and output interface.
Input devices may be manual switches and dials, such as on washing machines. A PCB is a base that supports the components that are soldered to it or fitted into sockets.
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Task: Each embedded system is built for a small range of specific tasks, unlike desktop and laptop computers that are general purpose and are capable of carrying out many different tasks.
Real-Time Systems: Embedded systems are real-times systems because they must ensure an immediate response in order for the system to react to different situations, e.g. when the button is pressed on a camera or when the brakes are applied in a car.
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