Topic 1.1 Systems Architecture

Topic 1.1 Systems Architecture

1. Cache Memory-The cache is where data for the Ram is held and where instructions frequently used by the computer are stored.

2. Fetch-Decode-Execute cycle- The FDE cycle is the process that a computer's CPU goes through to process every instruction. First the CPU fetches the data and places a value into the PC (Program Counter). Next the computer uses an instruction set to decode the information. Finally the computer executes any required action to complete the instruction.

3. What affects the performance of a CPU?

   • Clock Speed- The clock speed is the speed at which the CPU carries out an instruction/instructions. A CPU's typical clock speed is 2 GHz (Gigahertz) which means it can carry out the FDE cycle two billion times per second. Increasing the CPU's clock speed increases the amount of cycles per second the CPU can carry out, increasing its performance.
   • Number of cores- If the CPU only has a single core processor then it is only capable of processing a single instruction. If a CPU has 2 cores it is referred to as a dual core processor and can process two instructions per second. For example a single 2 GHz processor can only carry out 2 billion cycles per second whilst a dual 2 GHz processor can carry out 4 billion per second.
   • Cache-The larger the size of the cache memory (See other node), the more commonly used instructions and data the CPU is capable of storing. This allows a larger amount of instructions to be accessed quickly which boosts the CPU's performance for executing common tasks.

4. Von Neumann Architecture- This describes systems where the CPU runs programs that are stored in memory. These programs can consist of instructions and data that are stored as binary digits in memory addresses.

5. Key components in a system

   • Program Counter (PC)- The PC is responsible for storing the location of the next instruction in a program that is waiting to be fetched.
   • Memory Address Register (MAR)- The MAR is responsible for storing the location of where the data is being fetched or sent to in the memory.
   • Memory Data Register (MDR)- The MDR is responsible for storing the data that has been fetched from to or is waiting to be sent to the memory.
   • Accumulator (ACC) The accumulator is responsible for storing the results of calculations performed by the ALU
   • Current Instruction Register- The Current Instruction Register is responsible for storing instructions ready to be decoded by the ALU
   • Arithmetic Logic Unit (ALU)- The ALU is responsible for carrying out the arithmetic and logical operations in a computer instruction
   • Control Unit (CU)- The CU works with the CPU to decode instructions and control data flow within a system
   • Main Memory/RAM-The RAM is the main memory in the computer and stores data and programs that are in current use

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