The W83781D is a hardware status monitoring IC for personal computers, server computers, or microprocessor based systems. W83781D can be used to monitor several critical hardware parameters of the system, including power supply voltages, fan speeds, and temperatures, which are very important for a high-end computer system to work stable and properly. W83781D provides both ISA and I2C serial bus interface. A 8-bit analog-to-digital converter (ADC) was built inside W83781D. The W83781D can monitor 3 external thermistor temperature sensors, 5 positive analog voltage inputs, two inverting inputs (for monitoring negative voltages), and also three fan tachometer outputs. There is also one input for case open detection circuits. With the application software, the users can read all the monitored parameters of system from time to time. The users can set up the upper and lower limits of these monitored parameters to activate two programmable and maskable interrupts. An optional beep tone could be used as warning signal when monitored parameters are out of the preset range. Additionally, 5 VID inputs are provided to read the VID of CPU, if applicable. This is to provide the Vcore correction automatically. Also W83781D uniquely provides an optional feature: early stage (before BIOS was loaded) beep warning. This is to detect if the fatal elements present (Vcore, +3.3V) fail and the system can not be booted up.