The laws of thermodynamics spell out the fate of your computer. Waste energy manifests itself as heat, the random movement of molecules. Some random events are a bit more extreme than others and result in the microscopic circuits separating or burning through. At that point your computer becomes little more than an interesting piece of shiny silicon suitable for a key chain fob. Most of the time heat manifests as semi-random lockups and failures, typically when the machine is needed most.

It should be obvious by now that heat and temperature aren’t as simple as they may seem. There are many sources of heat in your system. Once you know the cause and effects of heat in your system, you can go about eliminating it as a problem. Here’s what you need to know.

Core temperature
Core temperature is the temperature of the device (e.g., processor or hard drive) as measured on the inside. As such, core temperature is the critical factor. All of the temperature control devices inside your system are there to minimize core temperatures. There’s no need to install additional cooling if your core temperatures are acceptable.

Measuring core temperatures can be problematic, since external thermometers read only the surface temperature of the circuit. While there may be only a few millimeters of intervening material, with modern circuitry being measured in microns, these miniscule millimeters might as well be miles. Most processors are now equipped with a thermal diode that measures the temperature within the circuitry itself.

Different processors from even the same line can have widely varying acceptable core temperatures. Typical core temperatures are listed below along with the location of the manufacturer’s online records. Intel has not published an official maximum core temperature for Pentium IV processors due to the on-board thermal shutoff system. Other processor core temperatures are as follows:

  • Pentium III: 75-90 C
  • Pentium IV: 80 C (as indicated by developer data on Intel’s Web site)
  • AMD Duron: 70-100 C
  • AMD Athlon: 70-100 C
  • AMD Athlon MP/XP: 85-95 C

Devices other than processors can suffer from heat. For example, hard drives and memory occasionally suffer. Unfortunately, there’s little way to measure their core temperatures, which forces you to examine their environment.

Ambient temperature
Many people believe that ambient temperature is the temperature of their office, but in relation to a processor or video card ambient temperature refers to the interior of the case. Some motherboards have sensors that can monitor the case’s interior temperature, but if your computer doesn’t have this feature, a $5 digital indoor/outdoor thermometer with a sensor on a cord and a high/low memory will work as well. In general, case temperatures should be kept below 80 F.

Ambient temperatures are controlled with case fans. Proper fan design generally has an air-intake fan at the front of the case at the bottom with a rear exhaust fan near the top and as close to your processor as possible. This lets natural convection work in your favor as the warmed air rises. Accidentally reversing a case fan can significantly alter the case’s ambient temperature, especially when high-flow fans are in play.

Restricted airflow in the case is often the crux of case temperature problems. Ribbon cables and power connectors can create a barrier in the case. Using cable ties or rearranging the drive layout can open up airflow in the case. In some cases, you may wish to consider using rounded cables; however, these typically have reduced performance because the close proximity of the wires results in increased interferences. Consider using additional or higher power fans before switching a server to rounded cabling.

For thermal problems with memory or hard drives, there are heat sinks and cooling fans that can be mounted to provide additional protection. Some people even advocate using 2-inch ductwork to provide a direct thermal exhaust for overheating components. With the exception of large cases full of drives, this is rarely an option due to space constraints. Simply adding a large 80-mm fan in the correct place will often do the trick.

Environmental temperature
Environment temperature refers to the temperature that exists immediately adjacent to the computer. It does no good to have a room kept at 60 F if you have the computer in a sealed cabinet that skyrockets to 90 F. This is not an exaggeration; most computers are equipped with a 300-watt power supply, meaning that in worst-case scenarios your computer might as well be a 300-watt space heater—more if you leave the monitor on. That $5 thermometer is useful here as well.

A typical office temperature can vary by as much as 15 F, depending on location and the amount of sunlight coming through the windows. Computers are often kept under desks where the cool air from ceiling vents may not reach them. Of course, placing the computer in a closed location, such as between a wall and a desk, can also have a significant effect. If there is insufficient space for the case fans to pull in or vent out air, the computer might as well be in a sealed closet. Always make sure there is a minimum of 6 inches between the front or rear of the computer and a wall, desk, or other obstruction.

Monitoring temperatures inside the case
There are several software packages out there that can tap into your computer’s thermal diode. One of the most popular is Motherboard Monitor, a freeware program that supports dozens of motherboard chipsets. Motherboard Monitor can also monitor fan speeds and voltages, making it an excellent tool for identifying thermal problems due to failing fans or voltage fluctuations.

Most computer BIOSes are also able to access the sensors on your processor and motherboard. Unfortunately, this is of little value, as your system will not be under stress while you are in the BIOS. Of course, if your temperatures are high in low-stress conditions, then your computer is likely to have problems once you get around to doing work.

In addition, there are monitoring panels that fit in a 5.25-inch drive bay that include multiple thermometers and a front panel display. Many are multipurpose and include audio, USB, and Firewire ports. These vary significantly in quality and features, so you will need to research them carefully. While in most cases they are rather unnecessary, if you have a borderline temperature situation, monitoring it becomes easier when you only have to get within a few feet to read an illuminated LCD.