Reference articles on history, science, culture and more
Surprise meSurprise meSubscribe
Encyclopedia

System monitor

Component that monitors resources in a computer system

Wikipedia contributorsAdapted for Fathomly · View authors
3 min read
Source updated March 30, 2026

A system monitor is a hardware or software component used to monitor system resources and performance in a computer system. Among the management issues regarding use of system monitoring tools are resource usage and privacy. Monitoring can track both input and output values and events of systems.

01Overview

Software monitors occur more commonly, sometimes as a part of a widget engine. These monitoring systems are often used to keep track of system resources, such as CPU usage and frequency, or the amount of free RAM. They are also used to display items such as free space on one or more hard drives, the temperature of the CPU and other important components, and networking information including the system IP address and current rates of upload and download. Other possible displays may include the date and time, system uptime, computer name, username, hard drive S.M.A.R.T. data, fan speeds, and the voltages being provided by the power supply.

Less common are hardware-based systems monitoring similar information. Customarily these occupy one or more drive bays on the front of the computer case, and either interface directly with the system hardware or connect to a software data-collection system via USB. With either approach to gathering data, the monitoring system displays information on a small LCD panel or on series of small analog or LED numeric displays. Some hardware-based system monitors also allow direct control of fan speeds, allowing the user to quickly customize the cooling in the system.

The primary function of a few very high-end models of hardware system monitor is to interface with only a specific model of motherboard. These systems directly utilize the sensors built into the system, providing more detailed and accurate information than less-expensive monitoring systems customarily provide.

A system monitor displaying system resources usage
A system monitor displaying system resources usage

02Software monitoring

Software monitoring tools operate within the device they're monitoring.

03Hardware monitoring

Unlike software monitoring tools, hardware measurement tools can either located within the device being measure, or they can be attached and operate from an external location.

A hardware monitor is a common component of modern motherboards, which can either come as a separate chip, often interfaced through I2C or SMBus, or as part of a Super I/O solution, often interfaced through Low Pin Count (LPC). These devices make it possible to monitor temperature in the chassis, voltage supplied to the motherboard by the power supply unit and the speed of the computer fans that are connected directly to one of the fan headers on the motherboard. Many of these hardware monitors also have fan controlling capabilities. System monitoring software like SpeedFan on Windows, lm_sensors on Linux, envstat on NetBSD, and sysctl hw.sensors on OpenBSD and DragonFly can interface with these chips to relay this environmental sensor information to the user.

04Privacy

When an individual user is measuring the performance of a single-user system, whether it is a standalone box or a virtual machine on a multi-user system, access does not impede the privacy of others. Privacy becomes an issue when someone other than the end-user, such as a system manager, has legitimate need to access data about other users.

05Resource usage

When events occur faster than a monitor can record them, a workaround is needed, such as replacing event recording with simple counting.

Another consideration is not having major impact on the CPU and storage available for useful work. While a hardware monitor will usually have less impact than a software monitor, there are data items, such as "some descriptive information, such as program names" that must involve software.

A further consideration is that a bug in this domain can have severe impact: an extreme case would "cause the OS to crash".

06List of software monitors

Single system:

Distributed:

Watch videos about System monitorExplainers and documentaries on YouTube (opens in a new tab)

Sources and credits

This article is adapted from the Wikipedia article “System monitor”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

Images, from Wikimedia Commons:

Fathomly is not affiliated with or endorsed by the Wikimedia Foundation. Spotted a problem? Tell us.

Continue exploring

Related topics

Application performance management

In the fields of information technology and systems management, application performance management is the monitoring and management of the performance and availability of software applications. APM strives to detect and diagnose complex application performance problems to maintain an expected level of service.

Application service management

Application service management is an emerging discipline within systems management that focuses on monitoring and managing the performance and quality of service of business transactions. ASM can be defined as a well-defined process and use of related tools to detect, diagnose, remedy, and report the service quality of complex business transactions to ensure that they meet or exceed end-users Performance measurements relate to how fast transactions are completed or information is delivered to the end-user by the aggregate of applications, operating systems, hypervisors (if applicable), hardware platforms, and network interconnects.

I2C

I2C, alternatively known as I2C and IIC, is a synchronous, multi-master/multi-slave, single-ended, serial communication bus invented in 1980 by Philips Semiconductors (now NXP Semiconductors). It is widely used for attaching lower-speed peripheral integrated circuits (ICs) to processors and microcontrollers in short-distance, intra-board communication.