User manual

BIOS Setup
52
Test points codes
At the beginning of each POST routine, the BIOS outputs the test point error
code to I/O port address 80h. Use this code during trouble shooting to establish
at what point the system failed and what routine was being performed.
If the BIOS detects a terminal error condition, it halts POST after issuing a
terminal error beep code and attempting to display the error code on the port
80h LED display (diagnostic card). If the system hangs before the BIOS can
process the error, the value displayed at the port 80h is the last test performed.
In this case, the screen does not display the error code.
The routine derives the beep code from the test point error as follows:
1. The 8-bit error code is broken down to four 2-bit groups.
2. Each group is made one-based (1 through 4) by adding 1.
3. Short beeps are generated for the number in each group.
Example:
Testpoint 1Ah = 00 01 10 10 = 1-2-3-3 beeps
The following is a list of the checkpoint codes written out to the diagnostic port at
the start of each test.
The first beep code inside of the BIOS has 1-long and 2-short beeps. This
means that there is a problem with the graphic adapter.
POST
Code
(Hex)
Name Description
02h
VERIFY_REAL
IF <in port mode> THEN
Turn on A20
Reset Processor
ENDIF
03h
DISABLE_NMI
Disable non-maskable Interrupts
04h
GET_CPU_TYPE
IF <cold boot> THEN
Store reset DX value in CMOS
Determine CPU manufacturer and
type
Store CPU manufacturer and type in
CMOS
ENDIF
06h
HW_INIT
Reset all DMA controllers.
Disable all video controllers.
Clear any pending interrupts from the
RTC
Set up port 61h to speaker off and timer
gate enabled.