Code

Meaning

02

Flag test

04

Register test

06

System hardware initialisation

08

Initialise chipset registers

0A

BIOS ROM checksum

0C

DMA page register test

0E

8254 timer test

10

8254 timer initialisation

12

8237 DMA controller test

14

8237 DMA initialisation

16

Initialise 8259/reset coprocessor

18

8259 interrupt controller test

1A

Memory refresh test

1C

Base 64K address test

1E

Base 64K memory test

20

Base 64K test (upper 16 bits) for 386 systems

22

8742 keyboard self test

24

MC 146818 CMOS test

26

Start first protected mode test

28

Memory sizing test

2A

Autosize memory chips

2C

Chip interleave enable test

2E

First protected mode test exit

30

Unexpected shutdown

31

DDNIL bit scan failure

32

System board memory size

34

Relocate shadow RAM if configured

36

Configure EMS system

38

Configure wait states

3A

Retest 64K base RAM

3C

CPU speed calculation

3E

Get switches from 8042

40

Configure CPU speed

42

Initialise interrupt vectors

44

Verify video configuration

46

Initialise video system

48

Test unexpected interrupts

4A

Start second protected mode test

4C

Verify LDT instruction

4E

Verify TR instruction

50

Verify LSL instruction

52

Verify LAR instruction

54

Verify VERR instruction

56

Unexpected exception

58

Address line 20 test

5A

Keyboard ready test

5C

Determine AT or XT keyboard

5E

Start third protected mode test

60

Base memory test

62

Base memory address test

64

Shadow memory test

66

Extended memory test

68

Extended address test

6A

Determine memory size

6C

Display error messages

6E

Copy BIOS to shadow memory

70

8254 clock test

72

MC 146818 RTC test

74

Keyboard stuck key test

76

Initialise hardware interrupt vectors

78

Maths coprocessor test

7A

Determine COM ports available

7C

Determine LPT ports available

7E

Initialise BIOS data area

80

Determine floppy/fixed disk controller

82

Floppy disk test

84

Fixed disk test

86

External ROM scan

88

System key lock test

8A

Wait for <F1> key pressed

8C

Final system initialisation

8E

Interrupt 19 boot loader

B0

Unexpected interrupt before or after boot up.