CS paper 1 revision

CS paper 1 revision

1. CPU performance

   • Clock speed
     • If you don't have a fast clock speed you can't do as many instructions per second
     • Clock speed is measured in Hertz (Hz) the typical speed is around 3.5GHz (3,500,000,000)
   • number of cores
     • each core is an extra instruction the computer can process at a time
     • Having more cores gives you a faster speed e.g. if you have 4 cores it increases the speed by 4x the amount you would have at 1 core
   • Capacity of Cache Memory
   • The control unit sends a pulse at a constant rate to start the next action.

2. Von Neumann architecture

   • registers are very fast but small memory with a specific purpose
     • the MAR holds the address of the memory location where data/instruction is to be fetched or stored
     • the MDR holds the data/instruction that has been fetched from memory or is going to be written to the memory
     • ACC (Accumulator holds the results of calculations made by the ALU
     • PC (Program counter) holds the address of the memory location of the next instruction. increments by 1 at the end of each fetch-execute cycle
     • Cache provides fast access to frequently used data and instructions.
     • ALU does arithmetic and logic calculations

3. Memory

   • RAM is primary memory which is able to be accessed randomly
     • RAM is expensive
   • Virtual memory is secondary memory used when the RAM is full
   • ROM is non-volatile read only memory
   • Cost per GB / How much data can be stored / how robust is the device / how fast can the device read / write memory

4. Network topologies

   • All instructions in a star topology are sent through the central hub/switch
   • In a mesh topology each device is connected to another without a central hub or switch

5. Protocols

   • TCP / IP - internet communication and reliable data transfer
   • HTTPS - encrypted web communications.