Acer Power ST Aspire T300 Service Guide - Page 56

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: T Microprocessor with built-in numeric co-processor and cache memory subsystem T Direct Memory Access (DMA) controller T Interrupt system T Three programmable timers T ROM subsystem T RAM subsystem T RTC RAM subsystem and real time clock/calendar with battery backup T Onboard serial interface controller T Onboard parallel interface controller T Embedded hard disk interface and one diskette drive interface T Keyboard and auxiliary device controllers T I/O ports T PS/2-compatible mouse port T PS/2-compatible keyboard port T Serial ports T Parallel ports T USB port 50 Chapter 4