I/O Management Flashcards
How is communicating with I/O devices handled?
Communication takes place over a cable known as a Bus, and is operated by Controllers.
What are the 4 types of registers used in I/O communication?
Data-In register, Data-out register, Status Register, Control Register
what is stored in the Control Register?
Commands to the device such as save, write, transfer, and read commands.
How does Port based I/O work?
Special Instructions are used to transfer a small number of bytes to an I/O bus address
How does Memory-Mapped I/O work?
Standard Memory Instruction used by treating the device as memory and writing/reading from the location.
What is Polling?
CPU checks controller status, when status is ready CPU writes to Data Out register then Controller. CPU is much faster than I/O so most Poll’s are unsuccessful.
What are I/O Interrupts?
When the I/O device wants to give an input its send san interrupt to the CPU in order to initiate the appropriate process.
What are I/O Interrupts?
When the I/O device wants to give an input its send san interrupt to the CPU in order to initiate the appropriate process.
In which circumstances is polling appropriate?
If the controller and device are fast in relation to the CPU, if the I/O rate is high, if some I/O data can be ignored, if the CPU is not engaged in other processes.
How are large data transfers handled?
These are inefficient if done byte by byte, this work is offloaded to a special purpose processor (Direct Memory Access Controller) so that the CPU can handle other processes.
How does the Direct Memory Access Controller work?
CPU writes a command block to memory specifying source and destination of transfer. DMA controllers can handle multiple transfers at the same time.
How do Device Drivers Function?
Device Drivers hide the differences between various device controllers by defining an interface between the OS and I/O devices. Device Drivers are loaded as modules into the kernel.
Which devices are Character I/O devices?
Keyboard, mouse, microphones, and speakers
How is data sent to Character I/O’s?
Data is sent in a stream of bytes. Characters must be processed in the order they arrive in the stream.
Which interfaces are used by Character I/O’s
Get operation, Put operation, Libraries for line-by-line access.