Computer Science Revision

Computer Science Revision

1. Computer Performance

   • Cache
     • Cache is only a small amount of memory.
     • Cache is used for temporary instructions that the CPU would be likely to use.
     • Cache is graded in 3 levels, L1, L2 and L3
   • Cores
     • Each core includes an ALU, a control unit and a control unit.
     • If a CPU has more cores it will have more power and energy to run quicker.
   • Clock speed
     • The clock speed is how quick a computer will run. This is measured in megahertz or gigahertz.
     • If a CPU has a clock speed of 2 gHz the CPU can perform 2 billion cycles per second.
   • Processor
     • The two main types of processor is CISC and RISC.
       • Instructions
       • Physical size
       • Speed
       • Energy consumption
       • Design
       • Cost
     • The majority of computers and laptops use CISC and smartphones and tablets use RISC.

2. Memory

   • Flash Memory
     • Flash Memory is non-volatile so data isn't deleted when the system is turned off.
     • Flash memory is slower than RAM
     • A USB stick is an example of flash memory, it can be used as external secondary storage.
   • ROM
     • ROM stores the data and instructions for a computer system to be run.
     • An example of a program that is stored in the ROM is BIOS (Basic Input Output System
     • BIOS checks that the hardware in the computer system functions correctly.
     • BIOS runs a 2nd prgram which boots up the computer's operating system from the hard drive to the RAM.
     • BIOS is always needed in the computer system therefore it is stored in the ROM.

3. Protocols

4. Secondary Storage

   • Solid state storage
     • Uses microchips instead of magnetised disks. Has no moving parts
   • Magnetic storage
     • Has magnetic plates that run at a very high speed.
   • Optical storage
     • It is read and written by lasers
   • Secondary storage is non-volatile. So data wont be lost when they computer system has no power

5. Networks