Knowledge Organiser 1 : Systems Architecture
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The purpose of the CPU | To manage basic operations of the computer. To be the ‘brains’ of the computer |
The main components of the CPU | Control Unit. Arithmetic Logic Unit. Registers. Cache |
Von Neumann Architecture | The architecture that allows for the storage of instructions and data in the same location |
The FDE Cycle | The cycle the CPU continuously carries out to process instructions |
Binary | The number system used to store instructions and data in the computer |
The role of a register in the CPU | It is a place to temporarily hold data and instructions as they are being processed by the CPU. |
The PC | The Program Counter keeps the address of the next instruction to be processed |
The MAR | The Memory Address Register is used to tell the CPU where to locate data in Main Memory |
The MDR | The Memory Data Register is used to store data that is fetched from Main Memory |
The ACC | The Accumulator stores results of logic operations and calculations used during processing |
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The Control Unit has two functions | (1) Sending signals to control the flow of data and instructions, and (2) decoding instructions |
Cache memory | A small section of extremely fast memory used to store commonly used instructions and data. It is useful as the CPU can access the (fast) cache directly. L1 cache is closest to the CPU, L3 cache furthest |
The ALU has the following functions | It carries out mathematical operations / logical operations / shifting operations on data; for example multiplication, division, logical comparisons |
An Address | This is a location in he Main Memory (RAM) that stores data or instructions in the Von Neumann Architecture |
Buses | Transfer information between the CPU and Main Memory (and other places). For example the Address bus carries memory addresses between the CPU and the RAM |
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The F-D-E Cycle repeatedly cycles | ��� |
The Fetch Stage | The address is generated by the Program Counter (PC) and is carried to the Memory Address Register (MAR) using the Address Bus. The PC then updates and stores the next memory address, ready for the next round of the cycle. The data or instruction that is in that memory location is placed on the data bus and carried to the processor and is stored in the Memory Data Register (MDR) |
The Decode Stage | The data or instruction is then the Memory Data Register (MDR). decoded to find out if it is a piece of data or if it is an instruction to do something such as ADD, STORE, SWITCH, REPEAT etc. |
The Execute Stage | The CPU performs the actions required by the instruction. If it is an instruction to control input or output devices the Control Unit will execute the instruction. If it is a calculation then the Arithmetic and Logic Unit (ALU) will execute the instruction. The results of any calculations are recorded in the Accumulator. |
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Cores | CPUs with multiple cores have more power to run multiple programs at the same time. |
Clock Speed | The clock speed describes how fast the CPU can run. This is measured in megahertz (MHz) or gigahertz (GHz) and shows how many fetch-execute cycles the CPU can deal with in a second. |
Cache Size | The more data that can be held in the cache, the shorter the trips the electric pulses need to make so this speeds up the processing time of each of those billions of electrical signals, making the computer noticeable faster overall. |
Definition | A computer system which forms part of an electronic device |
Re-programmable | Not for different purposes but firmware can sometimes be upgraded |
Reasons | They are cheaper to make and smaller than a General Purpose Computer |
Examples | Washing machine, Smart Oven, Car Engine, Pacemaker |
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