Polling vs Interrupt: Difference and Comparison

To keep an electronic device like a computer safe and avoid any problems that might occur, a few things and steps must be taken. When a device completes a certain task, the user assigns it, and the device performs it and finds out whether the task is completed.

There are ways that a user can use to find it out. These ways include 1. Polling, and 2. Interrupt.

The user either polls the device or it can use interrupts.

Key Takeaways

  1. Polling refers to the process of continually checking the status of an input or output device. At the same time, an interrupt is a signal that temporarily stops a running program from executing a specific task.
  2. Polling is more suitable for small systems with few devices, whereas interrupt is more efficient for larger systems with multiple devices.
  3. Polling can lead to high processor utilization while interrupting can improve the overall system performance by reducing processor load.

Polling vs Interrupt

The process of checking whether the device needs maintenance or not is called polling. The hardware involved in this procedure is low-level. It is a time-taking procedure. A polling process has two major steps. An interrupt is a type of hardware mechanism. Interrupts are of two types which are hardware and software interrupts.

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Polling vs Interrupt

The process in which the device is surveyed to ensure that there is any need for servicing is known as polling. It is a coeval procedure.

It is also considered a polled I/O or software-driven I/O. In the polling process, an external device is used to check the condition of the computer.

The process is continued until the device is ready, and if the device is not ready, it is shifted to a different task. The process has its independent properties, advantages, and disadvantages.

The hardware mechanism which notifies the device whenever it requires servicing is known as an interrupt. It notifies the computer whenever it requires to be attended by software.

It makes sure the ongoing task is completed on time. This process is temporary only when the problem is not serious.

If the problem is not serious, then the device returns to its activities.

Comparison Table

Parameters of ComparisonPollingInterrupt
MeaningThe concurrent process in which the device is surveyed to ensure any need for servicing is known as polling.The hardware mechanism that notifies the device whenever it requires servicing and needs to be attended by software is an interrupt.
Type ofProtocolHardware mechanism
Occurence At regular intervals of time.At any instance of time.
DeviceThe device is mended by the CPU.The device is overhauled by interrupt handlers.
Form of indicationCommand ready bit is used to inform the device.The request line is used to inform the device.

What is Polling?

The process in which the device is surveyed to ensure that there is any need for servicing is known as polling. It is a coeval procedure.

It is also considered a polled I/O or software-driven I/O. Low-level hardware is involved in this process.

It can take a lot of time if multiple devices are to be checked and surveyed.

The process of polling takes place in two steps, namely, host actions and controller actions. In host actions, the busy-bit is completely read by the host.

Once the busy bit is cleared, the command-ready bit is set to 1 by the host. Before setting the command-ready bit to 1, the command is written to the command register by the host.

The second step is the controller actions. In this step, the command-ready bit is already set to 1, and this is noted by the controller.

The controller then puts the busy bit to 1. The controller reads and performs the I/O operations after reading the command register and ensuring the presence of a write bit in it.

The operations are cleared and are shown to be successful.

Polling can be used to control the information sequence of elements involved in measuring contexts and also their execution. It can be used to administer the time of the processor along with other resources in multitasking operating systems.

Although the probability that the data can be wasted is much higher in polling.

polling

What is Interrupt?

The hardware mechanism which notifies the device whenever it requires servicing and needs to be attended by software is known as an interrupt. It notifies the computer whenever it requires to be attended by software.

It makes sure the ongoing task is completed on time. It is a type of hardware mechanism.

There are two types of interrupts, namely, hardware interrupts and software interrupts. In hardware interrupt, external hardware notifies the condition of the hardware.

In software interrupt, a processor requests the interrupt when a certain condition takes place. A particular interrupt handler ought to be associated with a software interrupt.

The software interrupts can be either intentional or unexpected. Special instruction is induced to cause a software interrupt intentionally.

Program execution errors that take place can cause unexpected software interruptions. Based on the triggering methods, there are two types of interrupts: level-triggered and edge-triggered.

The occurrence of interrupts results in increased CPU efficiency, and the CPU’s waiting time is decreased. The wastage of the instruction cycle is also stopped because of interrupts.

Some disadvantages of interrupts are that the CPU has to carry out a lot of tasks as it has to return to its previous program.

interrupt

Main Differences Between Polling and Interrupt

  1. In polling, the performance of the microcontroller is poor. On the contrary, in interrupt, the performance of the microcontroller is great.
  2. In polling, all the processor cycles are wasted while checking the device. On the other hand, in interrupt when a certain device interrupts a processor, the processor is disturbed.
  3. In polling, the CPU is put on hold. On the other hand, in interrupt, the CPU is called if required.
  4. Polling takes place at regular intervals of time. On the other hand, interrupt takes place at any instance of time.
  5. Polling is a type of protocol. On the other hand, interrupt is a type of hardware mechanism.
References
  1. https://link.springer.com/chapter/10.1007/978-1-349-16651-0_9
  2. https://ieeexplore.ieee.org/abstract/document/558057/

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