CPU

CPU

1. It's the brain of the computer

2. Components

   • Control unit
     • Manages the fetch-execute cycle
     • Controls the flow of data
   • Arithmetic and logic unit
     • Does all the calculations
     • Performs logic operations
     • Has the accumulator
   • Cache
     • Faster than RAM and slower than registers
     • Stores regularly used data
     • Higher the capacity, the lower the speed
   • Program Counter
     • Holds the memory address of the instruction for each cycle
   • Memory Address register
     • Holds the address for the next data or instruction
   • Memory Data Register
     • Stores the actual data or instruction being used

3. Fetch-execute cycle

   • Copy address from PC to MAR. Copy instruction from MAR to MDR.
     • Decode then execute the instruction

4. Embedded Systems

   • Computers that are built into another device for a single purpose
     • Dishwashers, sat-nav, planes
   • Cheaper and more efficient

5. Memory

   • RAM
     • Volatile
     • Slower than cache, faster the 2nd storage
     • Stores all things being used
   • Virtual Memory
     • When a computer needs more memory, it moves data to and fro 2nd storage and RAm to get more space
     • Makes the computer really slow
   • ROM
     • Stores the boot-up sequence
     • Volatile
   • Secondary storage
     • Hard disk drives
       • Internal storage
       • Stored magnetically on disks
       • Made of stacked disks
     • Solid State Drives
       • Type of flask memory
       • No moving parts
     • Optical Discs
       • DVDs, CDs
       • Not damaged by water and portable
     • Magnetic Tapes
       • Used for achiving
       • Require a special drive to read/write

6. Performance

   • Clock speed
     • Amount of instructions per second
     • Measured in Hz
     • Overclocking increases clock speed but can overheat the computer and damage it
   • Cache size
     • More data, faster because cache is faster than RAM
   • Number of cores
     • More cores, more instructions can be carried out
       • Faster to process data
   • More RAM
     • Less reliant on virtual memory

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