User`s manual

67
Power On Self Tests (POSTs)
When you turn on system power, the BIOS performs a series of tests and initializations. Each test or
initialization step is identified by a numeric "POST" code written to I/O address 378H. These codes
can be displayed using a commercially available "POST code display board". The following table
lists the POST codes expressed in hexadecimal, with their corresponding meanings.
POST code list
Code Meaning
00H CPU validation
01H CPU test
02H Component default programming
03H Timer initialization
04H Refresh line test
05H BIOS EPROM test
06H Keyboard controller test
07H First 64K RAM test
08H EEPROM test
09H 0F0000H-0FFFFFH shadow memory test
0AH DMA and interrupt controller initializations
0BH Video device test
0CH Timer #2 test
0DH DMA controller #1 test
0EH DMA controller #2 test
0FH DMA page control registers test
10H Interrupt controller #1 test
11H Interrupt controller #2 test
12H Shutdown byte test
13H Interrupt line 0 test
14H Keyboard test
15H Protected-mode switch test
16H Base memory size
17H Expanded memory size
18H Base memory test
19H Expanded memory test
1AH Co-processor test
1BH Real Time Clock test
1CH IRQ line test
1DH Parallel port test
1EH Floppy disk test
1FH Harddisktest
20H Serial port test
21H Mouse test
22H Shadow RAM test