Shared Knowledge

"PC - BYO and DIY Improved Cooling Tips"

"PC - Sources of Heat and How to Monitor"

6 April 2009


Summary: most modern personal computers (PC) have thermal sensors installed on the motherboard that can be read or monitored by either manufacturer or free software. Use software to check the internal temperature of your PC.




Major sources of heat inside a PC's case include: the processor chip; memory; voltage regulation circuitry on the motherboard; the AGP or PCI video board; disc drives and the power supply.


Typical heat ranges by component:

If a PC is "idling", none of the above devices give off much heat but stress the system by running an application like: a virus scan; a video game; Tivo desktop download; SETI or video processing and these components can heat up quickly. Or if the case has insufficient air exchange from outside to inside and inside to outside, temperatures can climb.

To give you idea of the temperatures (all in Fahrenheit) associated with each device:

                            Idling      Normal Range   Getting too Hot   Overload and Dangerous

Processor chip:     < 100           < 125              125 - 154                  > 154

Memory:               < 90             < 90                90 - 122                  > 122

Motherboard:        < 90             < 90                 90 - 122                  > 122

Hard Drives:         < 90            < 100               100 - 122                  > 122

Once upon a time when PC components were much slower than they are now, heat was not so much of an issue, but now heat can kill a processor, video board or hard drive.

To prevent permanent damage to the processor chip, modern processor chips have a temperature sensor built right into its circuitry and can actually shut down the entire system if the processor gets dangerously hot. Many folks experience "random shut downs" and do not understand that it is a thermal issue with their PC.

Finally, all above is good reference but most folk's PC provides no indication of interior case component temperatures other than some higher end video boards, which do provide a video processor temperature read out in their control panel software.

Most modern motherboards do have thermal sensors built into them. Most modern hard drives support S.M.A.R.T, which provides all sorts of information about a hard drive but again, most PC's do not have software to read thermal sensor or hard drive data.


Thermal monitoring software:

What I use and recommend is a free application called SpeedFan4.7. This free software reads all embedded motherboard thermal sensors as well as all S.M.A.R.T data from all hard drives. It is a very nicely designed piece of software that even allows a user to set thermal alerts such that when a thermal sensor goes above a user defined temperature, an alert is visually issued to the user. So far, I have not found a PC Speedfan does not work on but its functionality does vary with motherboard or laptop.

If you do install SpeedFan, be sure to calibrate displayed temperatures before accepting them as truth. Calibrate? When a system is cold or has set for some time turned off, when you power it up and execute Speedfan immediately, the CPU may report that it is at 90 or more degrees F. but since you just turned the system on, the cpu or any monitored component can not be much above room ambient air temperature. So to calibrate, you use the "Advanced" function of Speedfan to provide a temperature offset for each monitored device. If at start up the CPU is being reported to be at 100 degrees F, you use the advanced function to set in a -20 degree offset so the temperature of the CPU reads 80 degrees or about ambient air temperature plus a small safety margin. You ten apply an offset to each monitored component if its "start up" temperature is higher then room ambient.

Most Intel motherboards support what Intel calls "Active Monitor". Like Speedfan, it provides read outs of various temperatures and power supply voltages. It however, does not support S.M.A.R.T and does not allow for temperature offset and Intel clearly says that the temperatures reported by Active Monitor are not to be used in developing a thermal solution.



Click here for more DIY PC Cooling Tips


Ron - Shared Knowledge Home