How to Monitor CPU Temperature

Excessive heat damages electronics. Monitoring the temperature of your CPU and other computer components can help you keep them running properly. To make the most of monitoring software, you will need to ensure you have ACPI functionality enabled in your motherboard BIOS.

Why CPU Temperature is so Important

When the first affordable PCs were offered to the general public in the early 80's, system engineers and designers took in consideration what heat was emitted by system components and ensured their case and cooling designs handled the appropriate amount of heat so system damage or instability was rarely an issue. These PCs were not very configurable, and could not easily be modified or customized by the end user, except for memory limits and number of floppy storage devices. Most peripherals were external, so they didn't really add heat issues to the base system, and those that were internal were low power, and low bandwidth technologies. This was acceptable to the public at the time, since not many people felt the need to modify their PCs.

In the late 90's, the temperature bubble burst. Heat was increasing by leaps and bounds in newer systems that were far more complex than their predecessors.

Semiconductor Companies Producing Sensor Chips

Nearly complete information on sensing products, including documentation for APIs and other software interactions and data sheets are available from vendor web sites. The most prominent players in the sensor market are:

• Analog Devices
• Dallas Semiconductor
• Maxm
• National Semiconductor

Polling Sensor Circuits to Display Environment Data

As a user, normally you would use your system's BIOS configuration menus, or install monitoring software. As a developer, you would develop software using APIs that are developed to interact with system BIOS or the various system buses on your machine. Sensor controls are almost always connected to the computer's IDE bus or SMBus infrastructures, and can be accessed using the standard APIs for those buses.

Overclocking and Overvolting

Overclocking is the process of turning up the processor clock or multiplier value of a processor unit on the motherboard, attempting to get the highest possible clock and multiplier value without compromising system stability. Modern processors are often multiplier locked, preventing a user from just changing the bus multiplier, and introducing negligible additional heat to the system. Only the actual processor clock value can be changed on these CPUs, generally having a wider effect on system heat and stability.

Increasing the voltage values, or overvolting, allows the processor to handle its logic gates more reliably. A significant side effect of overvolting is increased heat emission.

Overclocking and overvolting your systems can have negative effects on the life span of your system, so be sure you know what you are doing when you attempt them. You could end up permanently damaging your hardware.

First Generation Monitoring Solutions: Monitoring Temperature in System Bios

The first generation of CPU temperature monitoring software packages merely displayed the CPU temperature value. No alarms, events, or actions could be defined, it was merely a display only technology. If action was required the user would have to notice that the temperature was at a critical state, and have to do something about it. If the user wasn't watching, the system could easily overheat and cause system damage.

Unfortunately, users aren't always at the console all day looking at temperature values, so this was only useful during diagnostics and testing periods when technicians knew there was a likelihood for temperature issues. It did help significantly with testing and burn-in periods, but beyond this, it was mostly just a data point a user might poll for a piece of mind.

Second Generation Monitoring Solutions: Sensor Circuits for Monitoring Temperature

Sensor circuits of the second generation of monitoring solutions have the ability to regulate and control environmental conditions automatically, so these are adequate enough to keep your system stable when heat is an issue, and quiet when it isn't.

Third Generation Monitoring Solutions: Hardware that Allows Software to Monitor and Modify State

The newest generation of CPU temperature monitoring software interacts directly with motherboard sensor and fan control circuits to attempt to control and adjust the system environmental conditions. Many of the motherboard manufacturers offer this software for free (Abit's microguru and Asus' PC Probe), because they are specifically targeting the custom and high performance system builders. In fact, Abit has an excellent LCD panel that you install in a 5.25" 1/2 height drive bay that allows you to monitor and even control your processor and environmental settings using a simple button interface!

Third Party Monitoring Software

Not all motherboard vendors provide software to display and control system environmental resources. Even when they do, sometimes the software is functional, but poorly developed, clunky, unreliable, or may not play well with other installed system software. Aside from this, not all vendors use the same sensor solutions on their boards, or between multiple boards they produce. Also, many motherboard vendors don't put as many fan controller connections as you would prefer to have in your system, so you may want to install a fan controller card or additional environmental control components that are outside of your motherboard's control. To cope with this, many developers have been providing software solutions to give you an integrated control solution.

Most monitoring software will automatically detect and configure the proper sensors for your motherboard. Some have a drop down list of motherboards that you can select from, and others simply have a list of motherboard sensors to select from. If you have questions about which motherboard sensors your motherboard has, check your motherboard or system documentation, or contact your system vendor.

Free Windows CPU Temperature Monitoring Software

Second Generation Monitors

• Motherboard Monitor is an excellent program that handles a wide variety of motherboards and sensors, but is no longer in development. Since the package will never be released open-source, as time goes on, it will be less and less usable. Thanks for your efforts, Alex van Kaam!
• If you have an Intel motherboard or motherboard based on an Intel Chipset, you can utilize the Intel Active Monitor.

Third Generation Monitors

Most third generation monitor packages are only available through motherboard manufacturers at this point, but a few third party packages re available for download.

• SpeedFan is a freeware program that monitors voltages, fan speeds and temperatures in computers with hardware monitor circuits. What really sets SpeedFan apart is that it can change fan speeds (if supported by your computer's hardware) according to the temperatures measured inside your PC. SpeedFan makes it possible for you to run your PC to run very quietly, while also running it safely.
• Hmonitor is a cross breed between second and third generation monitoring software. The professional version of the Hmonitor software can preempt a change in CPU frequency or fan speed based on an event.

Free Linux CPU Temperature Monitoring Software

Linux has had a few effective temperature monitoring packages out there for the last few years. It should be easy to install and configure such software programs for users who are well-versed with the Linux operating system. Most of these packages require a recent release of the Linux kernel.

Second Generation Monitors

• lm-sensors has the capability to detect, display and configure monitoring parameters for your Linux system.
• If you want to monitor many system resources at a glance, or control how the display of that data is provided, you could use GKrellM. GKrellM is just a visual framework for the environmental control functions of Linux, so you will need to have previously install "lm-sensors" to get it fully functional.
• KSim is a package that combines the sensing capabilities of "lm-sensors" with the visual controls of "GKrellM". KSim is a plugin based system that lets you monitor and display only those components you feel are important.

Third Generation Monitors

An integrated third generation application for system sensor monitoring and control has not been released to the public as of yet, but there are some alternatives if a user has the adequate motivation, knowledge and links with the Linux developer community.

• The Sourceforge ACPI Project is an ACPI framework and utilities set for Linux that can be used to monitor and control system environmental resources.

Free FreeBSD CPU Temperature Monitoring Software

FreeBSD has an application in its ports system that will allow you to monitor your onboard sensors.

Second Generation Monitors

• lmmon is an ncurses based application that samples the sensor status every second, and displays it on the screen. The software can be configured to output simple text and can be utilized by system management and alerting systems like the NET-SNMP package or other external programs.

Apple OSX CPU Temperature Monitoring Software

Apple Computer has always led the industry in providing the user's low level controls and details on their hardware that most manufacturers would consider unnecessary, or even foolhardy. Apple has continued this practice by providing access to more hardware monitoring sensors than other comparable systems provide. So far, all software releases for monitoring on OSX are second generation solutions.

Second Generation Monitors

• If you are only concerned about temperature sensors in your OSX system, the Temperature Monitor is a freeware application that will monitor and display all temperature related systems on your computer. If you want to monitor and display non temperature related sensors, you can purchase the full version of the Hardware Monitor software.

Modern users want to control and customize their systems to a greater degree today than ever before. Because of this, monitoring your system's sensor resources is critical for helping make what was previously a tedious, time consuming and technically challenging possible for the everyday user.