1.1 | Systems Architecture

• A computer is an electronic device which takes input, processes data, and delivers output.
• Memory is hardware that is used to store data that a CPU needs access to.
• The CPU processes data and instructions through the FDE-cycle and controls the rest of the computer system.
• The Control Unit sends signals on how data should move around the CPU. The CU is also responsible for fetching, decoding and executing instructions.
• The Arithmetic Logic Unit performs the calculation and logical decisions. It also acts as a gateway between primary memory and secondary storage.
• Cache memory is high-speed random access memory built into the processor. It is a temporary store of instructions which are likely to be reused.
• The registers include: Memory Address Register, Accumulator, Memory Data Register, Program Counter
• Registers are small amounts of high-speed memory within the CPU.
• The Memory Address Register is the register that tracks the RAM address of the instruction that is to be fetched.
• The Program Counter (PC) holds the address of the next instruction to be executed.
• The Memory Data Register stores the instruction that has been transferred from the RAM to the CPU.
• The Accumulator stores the result of the mathematical or logical calculations.
• The instructions are fetched from RAM to be decoded and executed by the CPU. (FDE cycle)
• FDE Cycle | 1. The Program Counter displays the address in RAM of the next instruction to be processed. This value is copied into the MAR (Memory Address Register).
• FDE Cycle | 2. The PC register is incremented to prepare for the next instruction to be fetched.
• FDE Cycle | 3. The CPU checks the address in the RAM which matches the address held in the Memory Address Register.
• FDE Cycle | 4. The instruction in the RAM is transferred to the MDR.
• FDE Cycle | 5. The instruction in the MDR is decoded by the Control Unit.
• FDE Cycle | 6. The cycle repeats and checks the program counter again for the next instruction.
• Clock speed is the number of clock cycles per second that the CPU can complete. It is measured in Hertz.
• The cache size is the amount of RAM that is used to store frequently used data. A bigger cache means more data can be stored.
• If the number of cores is high, more tasks can be completed simultaneously.
• An embedded system is a small computer that forms part of a larger system, device or machine. An example of this would be a washing machine.