27 Sep Input/Output Device Characteristics

Please read the following. Instructions are at the end.

For this Discussion Board, before posting your primary response, please first read through the following sections.

Input/Output (I/O) devices are another important part of a computer. The six types of commonly used I/O devices are the keyboard, mouse, monitor, printer, magnetic disk, and thumb drive. An I/O module is a software program developed to control a specific I/O device. The I/O module is a critical architectural element of a computer system. The technique used to implement an I/O module’s function is called an I/O control. There are only three types of I/O controls.

Programmed I/O (also called polling I/O) is the most commonly used I/O control technique for any type of data that are exchanged between the central processing unit (CPU) and the I/O module of an I/O device. When the CPU encounters an I/O-related instruction, the CPU will issue a command to a corresponding I/O module, which is a set of instructions to perform the required I/O operations in the I/O status register. When the CPU issues a command to the I/O module, it must wait and check the status register in a busy loop until the I/O operation is completed, as indicated by the proper bit set in the status register.

Read this article on Programmed I/O to see more about program-controlled I/O.

Interrupt-driven I/O is the I/O control module that sends a program interrupt signal to the CPU for it to notice that the I/O activities of an I/O device need its attention for the I/O data transferring (I/O Techniques, n.d.b). When the time slot for the priority level of the I/O interrupt arrives, the CPU enters an interrupt service routine, which will complete the required I/O operations. The interrupt-driven I/O has to have hardware and software that are more complex but make for a far better use of the computer’s time and capacities.

Read this article on Interrupt Driven I/O of interrupt-driven I/O.

Direct memory access (DMA) is the I/O control that transfers data within the main memory and the external device without having to pass data through the CPU (I/O Techniques, n.d.a). It allows the CPU to complete other tasks in parallel as the DMA handles the data exchange between I/O devices and the main memory. Direct memory access is especially efficient when large volumes of data have to be transferred. For DMA to work, the CPU and DMA module must share a system bus. That is, the DMA module must use the bus only when the processor does not need it, or it must force the processor to suspend operations temporarily through a technique called cycle stealing.

Read this article on Direct Memory Access (DMA) of DMA.

Input/Output Device Characteristics

Any I/O device can be described using three qualities. To comprehensively describe any I/O device, it is best to use the behavior, communication partner, and I/O control categories to explain its characteristics. The following table includes the characteristics of some common I/O devices:

I/O Device Behavior Type Communication Partner Type I/O Control Type

Keyboard Input Human Programmed I/O or interrupt-driven I/O

Mouse Input Human Programmed I/O or interrupt-driven I/O

Monitor Output Human Programmed I/O or interrupt-driven I/O

Printer Output Human Programmed I/O or interrupt-driven I/O

Network interface Input or output Machine Programmed I/O, interrupt-driven I/O, or DMA

Disk (magnetic) Storage Machine Programmed I/O, interrupt-driven I/O, or DMA

Disk (optical) Storage Machine Programmed I/O, interrupt-driven I/O, or DMA

Primary Response

Please discuss the following:

• Based on what you have learned, what type of I/O control can be used for a printer? Why?

• DMA or interrupt-driven I/O can be used to control a thumb drive. Compare the pros and cons of these two types of I/O control when they are used to control a thumb drive.

To help you with your discussion of this, you can create a summary by using the following table template:

Type of I/O control to

control a thumb drive DMA Interrupt-driven I/O

Pros o First pro

o Second pro o First pro

o Second pro

Cons o First con

o Second con o First con

o Second con