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ICT lesson, 15 Feb Notes

0. Continuation on Clock Rate

- 5.1GHz (10^9) = 5100MHz (10^6) = 5100000KHz (10^3)
- Hz = Hertz
- Extra: NS and MS
    - NS (nano-second): 10^-9 second
    - MS (micro-seond): 10^-6 second

1. Word length

- A command will be converted to HEX to be passed on to PC
- e.g. ADD AX,3
    - ADD will become `0001`
    - AX will become `0010`
    - 3 will become `0011`
    - The command will be 12-bits.
- 64 bit = can store command that's 64 bits long.
- ADVANTAGES of larger bits:
    - Can store a larger value (because more bits)
        - Largest value 4 bits can store is `15` (`1111`)
        - The larger the bits, the more it can store
        - The larger the bits, the more commands it can do
        - The larger the bits, the more the built-in functions (Can do more complicated things easily)

2. Main memory

- Important compoment
- Hard disk -> Main Memory -> CPU
- Main memory is faster than hard disk but slower than CPU
- RAM can cache stuff, and hence make processing faster
    - e.g. Cache previous calculations
    - e.g. Cache datasets that will be used in the future
- CPU don't have enough storage to save stuff, and that's why we need RAM
- RAM = **[temporary]** storage / buffer for data and instructions to be processed by CPU
- RAM = **[volatile]** storage.
    - All things in RAM will be cleared once device is powered off.
    - Some RAM will clear data themselves
- RAM measuring unit = Gigabytes (till now)

- ROM = read only memory
    - Read-only, uneditable
    - Non-volatile
    - Loads basic tools that's necessary for operation of computer
        - e.g. BIOS
        - e.g. bootstrap program

- Cache Memory (within CPU)
    - Small storage
    - High data access rate
    - Fastest within all main memory
    - Usually kept small in storage size due to it being very expensive