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revision guide : 1.1 exam - Coggle Diagram
revision guide : 1.1 exam
CPU configuration
each time the clock ticks one FDE cycle takes place
clock speed is measured in hertz which is the unit of frequency and means "number of times per second" - typical modern computers work at up to 4GHz (4 billion instructions per second) - faster the clock speed the more instructions that can be executed every second
each core can fetch and execute cycles independently
cache memory can hold data that needs to be accessed quickly
CPU and RAM work together : when a program is loaded it is copied into RAM ,the CPU can then access both data and instructions : Data is transferred from secondary storage into RAM to be used by the CPU : Once data and instructions are in RAM they are then transferred to cache memory, in order to further improve data access speeds for the CPU
cache memory works as temporary storage the CPU can access quickly. Stores instructions and data that are used repeatedly or likely to be required for the next operation
The more data that can be stored in in cache memory rather then main memory the faster and more efficient the process Data that is likely to be required will be transferred to cache ready to be used
The larger the cache memory the more likely it is that the required data will already have been copied across from main memory. Cache memory is very expensive and while a mid -range laptop may have 8GB of RAM it is likely to have just a few KB of cache
Von Neuman architecture
memory data register (MDR) - stores data fetched from memory or to be sent to memory
memory address register (MAR) - stores the address of the location in memory for data to be fetched from or sent to
program counter (PC) - stores the address of the next instruction to be processed
accumulator (ACC) - stores the results of any calculations carried out by the ALU
Events in Fetch-decode-execute cycle (FDE)
Decode - the CPU decodes the instruction
Execute - the CPU preforms an action according to the instruction
Fetch - an instruction in the form of data is retrieved from main memory
Embedded systems are computers systems that have a dedicated function as part of a larger device. The main components of a computer system are either manufactured onto a single chip (a microcontroller) or separate circuits for processing and memory are combined into larger devices
processor cores - Each core can fetch and execute instructions independently so a multiple core processor can handle several instructions at the same time. While they these multiple cores can work on separate programs or parts of a program at the same time, this is only possible if the program has been written to take advantage of multiple cores. The task that the program is attempting must also be one that can split up into subsections to take advantage of multiple cores
CPU definitions
Control unit (CU) - coordinates the activity of the CPU by fetching and decoding instructions from memory and sending out signals to control how data moves around the parts of the CPU and memory, in order to execute these instructions
registers - memory locations within the CPU that hold data temporarily and can be accessed very quickly. Their role in the CPU is to accept, store and transfer data and instructions for immediate use by the CPU. Used during the FDE cycle
Arithmetic logic unit (ALU) - operations such as add, subtract, multiply, divide / logical operations such as AND,OR and NOT and the result of "less than" "greater than" "equal to" comparisons / binary shift operations (multiplication and division) / the ALU carries out the calculations and logical decisions required by the program instructions that the CPU is processing