Acer Aspire SA80 Aspire SA80 and Power S280 Service Guide - Page 81

Power-On Self-Test (POST) Before the computer can be used, all the components must be tested and initialized, and the operating system must be bootstrapped into memory. This process is know as the power-on Self test(POST), generally under the control of the BIOS. 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. During POST, system reports test or initialization failure through Beep codes, display error messages on screen(if available), or LED. The system halts when fatal error occurs. 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 73 Chapter 4