1.1 System architecture
- Created by: HMajid198
- Created on: 21-08-20 12:34
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- System architecture
- CPU
- Process data and instructions
- Controls the rest of the computer
- Controls hardware components
- Von Neumann architecture
- MAR - holds address of current instruction that is to be fetched or the address in memory in which data is to be transferred
- MDR - Holds contents found at address held in MAR or data which is to be transferred to primary memory
- PC - (program counter) holds memory address of next instruction to be fetched from primary memory
- ACC - (accumulator) holds data being processed and the result of processing
- Data and instructions in binary, stored in primary memory, instructions fetched one at a time in order and instruction is decoded and executed before fetching next
- Common CPU components
- Arithmetic logic unit - (ALU) performs arithemic and logic calculations
- Control unit - (CU) manages instructions in the CPU
- Cache - very fast RAM in the CPU (easily accessible) - temporarily stores data likely to be re-used
- Clock - sends out regular pulses to synchronise the computer's components
- Cores - processing unit within the CPU each capable of fetching, decoding and executing its own instructions
- Fetch decode execute cycle
- 1. Memory address held in the program counter is copied into the MAR
- 2. Address in the program counter increases by 1 (now holds address of next instruction)
- 3. Processor sends a signal along the address bus to the memory address held in the MAR
- 4. Instructions/ data held in that address are sent along the data bus to the MDR
- 5. Instruction/ data held in MDR is copied into the CIR
- 6. Instructions/ data held in the CIR are decoded and executed - results are stored in the ACC
- CPU performance
- Clock speed - number of pulses the CPU's clock processes generates per second
- Can be sped up by the user (overclocking) - can cause long term damage and can cause overheating
- More pulses per second = more FDE cycles can be performed
- Cache size - bigger the cache size, the less time the processor has to wait
- Number of cores - the more cores in a CPU, the greater the number of instructions that can be processed in a given space of time
- Clock speed - number of pulses the CPU's clock processes generates per second
- Embedded systems
- Embedded system - a small computer that forms part of a larger system - controls the device and allows a user to interact with it
- Examples: central heating, calculators, dishwashers, digital watches
- Not programmable by a user but software can be upgraded
- Advantages: cheaper to design due to limited features, require less power and do not need much processing power
- CPU
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