Power-On Self-Test (POST)
Each time you turn on the system, the Power-on Self Test (POST) is initiated. Several items are tested during POST, but is for the most part transparent to the user.
The Power-On Self Test (POST) is a BIOS procedure that boots the system, initializes and diagnoses the system components, and controls the operation of the power-on password option. If POST discovers errors in system operations at power-on, it displays error messages on screen, generates a check point code at port 80h or even halts the system if the error is fatal.
The main components on the main board that must be diagnosed and/or initialized by POST to ensure system functionality are as follows:
Microprocessor with built-in numeric co-processor and cache memory subsystem Direct Memory Access (DMA) controller
Interrupt system
Three programmable timers ROM subsystem
RAM subsystem
RTC RAM subsystem and real time clock/calendar with battery backup Onboard serial interface controller
Onboard parallel interface controller
Embedded hard disk interface and one diskette drive interface Keyboard and auxiliary device controllers
I/O ports
PS/2-compatible mouse port PS/2-compatible keyboard port
Serial ports Parallel ports USB port