SIW lets you monitor voltages, fan speeds and temperatures in computers with hardware monitor chips. SIW accesses S.M.A.R.T. info for those hard disks that support this feature and show hard disk temperatures too, if supported. SIW knows only few Asus/Winbond hardware monitor chips connected to the 2-wire SMBus (System Management Bus, a subset of the I2C BUS) Serial Interface .
For Intel Core and AMD K8 (AMD64) CPUs, SIW shows the die temperature. The temperature readings are very accurate as the data is collected from a Digital Thermal Sensor (or DTS) which is located in each individual processing core, near the hottest part.