Please enable JavaScript.

Coggle requires JavaScript to display documents.

Chapter 1 part two : Cache Memory, Chapter 1 : Part 3 - Understand I/O in…

- - - - Accessible by the processor via an I/O Module.
    - - Directly accessible by the processor.
- - - - Main Disadvantage:
        
        There is a fixed cache location for any given block,,,,Thus if a program happens to reference words repeatedly from two different blocks that map onto the same line,the block will be continuously swapped in the cache,the hit ratio will be low.
        
        CACHE HIT :Data found in cache.Results in data transfer at maximum speed.
  - - - There is flexibility as to which block to replace when a new block is read into the cache.
      - In Fully Associative Mpped Cache,each memory location can be in any cache block (a block is allowed to go anywhere in cache.
      - Overcome the disadvantage of direct mapping by permitting each main memory block to be loaded into any line of the cache.
      - There is no restriction on mapping from memory to cache.
      - Associative search of tags is expensive,so this type of mapping only feasible for very small size caches only.
- - - - Each character transmitter consists of a start bit,character bits,and stop bitss.
      - The first bit is called the start bit.it is always a 0 and is used to indicate the beginning of character.
      - Asynchronous serial transmission is character oriented.
      - The last bit called the stop bit is always a 1.In asynchronous transmission, binary information is sent to only when it is available and the line remains idle when there is no information to be transmitted.
- - - - Disadvantage- CPU is tied up for the duration of the transfer while doing a relatively simple task.
      - Advantage-Simple to implement
    - - If the CPU is faster than I/O module,there is wastage of CPU time.
      - When CPU issues a command to I/O module, it must wait until I/O operation is complete.
      - Data are exchanged between the CPU and the I/O module.
      - Programmed I/O refers to uing input and output instructions to transfer data between memory and the registers on a peripheral interface.
      - The CPU executes a program that gives it direct control of the I/O operation,including sensing device status,sending a read or write command and transferrinf data.
      - Is the method of transferring data between the CPU and a peripheral such as a NETWORK ADAPTER or an ATA STORAGE DEVICE.
      - The best known example of a PC device that uses programmed I/O is the ATA interface.
      - In general, programmed I/O happens when software running on the CPU uses instructions that access I/O address space to perform data transfers to or from an I/O device.
- - - - 2)The I/O DMA controller manages the enite transfer (possibly) thousand of bytes in length ),the number of bytes to transfer.
      - 3)When the DMA transfer is complete,the I/O controller interrupts the processors to let it know that the transfer is complete.
      - 1) The processor initiates the DMA transfer by supplying the I/O device address, the operation to be performed, the memory address destination / source, the number of bytes to transfer.