Please enable JavaScript.

Coggle requires JavaScript to display documents.

Devices and I/O (Architecture (Bus (Configuration (The CPU is generally…

- - - - Communication path between different devices
    - - Lower level bus where connections such as: SCSI, SATA, or USB are connected.
    - - Bus that connects the CPU to main memory
    - - The CPU is generally connected to the main memory via the memory bus. The memory bus is connected to the peripheral bus via a bus bridge.
      - The faster a bus is the shorter it is.
  - - - These instructions specify a way for the OS to send data to specific device registers
      - Example:
        
        "in" and "out" INS on x86.
        Caller specifies a register with data in it and a specific port which names the device. INS transfers data between the port and the register
    - - Hardware makes device registers available as if they were memory locations.
        To access a particular register:
        
        OS issues a load/read or store/write to the address
        
        Device routes the INS to the device instead of main memory
    - - Program-controlled I/O
        
        The device driver moves the data between memory and a buffer on the device.
      - DMA
        
        Device makes a request to transfer data,
        OS sets up DMA to grab data request
        DMA grabs data
        While data is being transferred from DMA to the other device the CPU is still available
- - - - Requires constant power to keep values
    - - Traps electrons in quantum "cage"
- - - - A circular hard surface on which data is stored persistently by inducing magnetic changes to it
    - - Concentric circle of sectors
    - - The component that reads/writes from the track
  - - - Seek Time
        
        The time it takes for the disk head to move to the appropriate track
        
        Seek distance
        
        The distance between the previous request track and the current request track
      - Rotational Latency
        
        The time the disk head has to wait for the desired sectors to rotate under the disk head
      - Transfer Time
        
        The time it takes the disk head to spin past the disk head
      - Request Service Time
        
        Request Service = Seek time + rotational latency + transfer time
  - - - Orders the queue of requests by tracks. Picking requests on the nearest track to complete first
      - Advantages
        
        This leads to shorter seek times
      - Disadvantages
        
        This can cause requests to starve
    - - Services the requests in the order they appear
      - Advantages
        
        Fair and simple to implement
      - Disadvantages
        
        Does not optimize seek time
    - - The disk head travels from the outer track to the inner track and back servicing requests as they appear. If a request appears while the head is servicing in one direction it will not back-track to get it. It'll get it on its return the other direction