What it does
SpeedFan is a freeware program that monitors fan speeds, temperatures and voltages in computers with hardware monitoring chips. SpeedFan can even access S.M.A.R.T. info for those hard disks that support this feature and show hard disk temperatures too, if supported. SpeedFan can even change the FSB on some motherboards (but this should be considered a bonus feature). At the lowest level, SpeedFan is an hardware monitoring software, but its main feature is that it can control the speed of the fans (depending on the capabilities of your sensor chip and your hardware) according to the temperatures inside your pc, thus reducing noise and power consumption. Several sensors, like Winbond's and ASUS AS99127F support fan speed changing, as well as others from MAXIM, MYSON, ANALOG DEVICES, NATIONAL SEMICONDUCTORS and ITE, but the motherboard manufacturer must have connected the relevant pins to some additional, yet trivial, circuitry. This means that if you have, say, a W83782D on a BP6 then you're ok, but not every motherboard with such an hardware monitoring chip will be able to change fan speeds.
SpeedFan can find almost any hardware monitoring chip connected to the SMBus (a subset of the I2C BUS), to the ISA BUS and to nVidia Video Cards. SpeedFan works fine with Win9x, WinME, WinNT, Win2k, Win2K3 and WinXP.
SpeedFan can be minimized to the tray and is compatible with Motherboard Monitor 5.

4.14 - fans are reset to 100% on exit even if using LOGOFF
- added support for S.M.A.R.T. drivers that do not fully report requested data
- charts properly show Fahrenheit, if needed
- german translation
- added full support for nVidia nForce 3 250
- added full support for LM86
- added full support for ADM1031
- added support for W83792D
- added support for Fujitsu-Siemens Hermes
- added support for more nVidia Video Cards
- now it can be selected whether pressing the X on the title bar causes SpeedFan to be minimized (EXIT from the icon menu always closes SpeedFan)
- added support for the third PWM on W83627THF