Computers

• Hardware are the physical components of a computer
• Software is instructions that tell hardware what to do
• Features of the von neumann architecture include:

  1. Fetch decode execute cycle
  2. 1 ALU 2 CU 6 Registers (/more than 1 registers)
  3. Data and instructions stored as binary in RAM
• Fetch:

  • Memory address of instructions to be fetched are stored in memory address register and sent down by address bus
  • Instruction fetched by data bus
  • Instruction stored in current instruction register
• Decode:

  Instruction decoded by CU and turned into opcode and operand.
• Execute:

  • Opcode and operand executed upon in ALU, decisions made
  • Result stored
• There are three types of buses:

  1. A ddress bus
  2. M emory bus
  3. D ata bus
• The address bus is unidirectional.
• The data bus transfers data from the CPU to the memory.
• The control bus transfers control signals from the CU to the other components of the computer.
• The Address bus transfers memory addresses from CU to memory.
• Examples of registers: (note to self: add more later)

  1. A ccumulator
  2. P rogram C ounter
  3. M emory A dress R egister
  4. C urrent I nstruction R egister
• Why is the CPU often referred to as the work desk or brain of the computer?

  It processes data & instructions (runs fetch decode execute cycles)

  It controls the rest of the computer system
• What is a microprocessor?


  type of integrated circuit on a single chip
• CPU performance is affected by number of cores and the clockspeed of each core.
• Clockspeed measure show many instructions each core can execute per second (otherwise, how many fetch decode execute cycles it can run)
• GigaHertz = 1 billion / second MegaHertz = 1 million / second
• Clock speed is measured in Hertz or Hz
• Multiple cores increase CPU performance as it can multitask (meaning multiple instructions can be executed upon simultaneously)
• Each core runs seperate fetch decode execute cycles.
• A dual-core processor has two processing units which means it can process twice as much data at once compared to single-core processors if all cores have the same clock speed.
• Embedded systems are systems that are smaller with limited specific functions built within a larger mechanical device or system.
• Embedded systems contain input, output, and run on firmware.
• Examples of embedded systems include: the flash in a camera, a microwave clock, windshield wipers, central heating systems
• Data storage pyramid represents capacity and CPU access speed in descending and ascending order, it goes as follows:

  Registers > Cache > Main memory > Secondary storage

  
• All types of primary storage are voltaile except for ROM
• ROM stores the boot up sequence of a computer.
• Primary storage is directly accessible to the cpu and has faster R.A.W speed/access speeds but are volatile.
• The main difference between RAM and ROM is that RAM can be written to whereas ROM cannot.
• Secondary storage is not directly accessible by the CPU and have slower RAW speeds/access speeds but are non-volatile.
• Without secondary storage all data in a computer would be lost after it is shut off
• RAM: stores data, instructions, software (including OS).
• Cache: stores frequently and recently used instructions and data.
• Registers; used for handling, controlling instructions/data in CPU's operations.
• The 3 main types of secondary storae are SSD, Optical, and Magnetic
• SSD: Solid State Drives - no moving parts, faster than HDD, more expensive, less capacity
• Optical Storage: CD, DVD, Blu Ray - has read only versions to distribute media, slower than SSD to write, cheap, susceptible to scratching, easy to transport, requires disk reader
• Magnetic Storage: Hard Drive, Floppy Disks, Tape - not as fast to write due to moving parts, high capacity capacity, cheap
• SSD uses nand gates with current flowing indicating a 1 and current not flowing indicating a 0
• Optical uses a laser to burn pits indicating 1 and land indicating 0