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DTK Post Procedures - Symphony 486 BIOS

Procedure

Meaning

Initialise Interrupt Controller

Check the PIC chips.

Initialise Video Card

Initialise DMA Controller

Initialise Page Register

Check the 74612 chips.

Test Keyboard Controller

Internal operations of the keyboard controller are tested (8042).

Initialise DMA Contr/Timer

All DMA registers and CMOS status bytes 0E/0F are cleared. The BIOS then initialises the 8254 chip. Check the DMS or PIT chips.

DRAM Refresh Testing

Base 64K Memory Testing

A walking-bit test of the first 64K of RAM address which is critical for the BIOS vector area to be initialised. Check for bad RAM chips or a data or address line.

Set System Stack

An area of memory is set aside by BIOS as a stack. Check bad DMA/memory.

Read System Configuration via 8042

e.g. the keyboard controller. Check for incorrect setup or bad keyboard controller or CMOS chip.

Test Keyboard Clock and Data Line

The keyboard's ability to handle the A20 line is tested as well as its internal clock. Check the keyboard controller or a bad address line.

Determine Video Type

Check RS232/Printer

Test serial/parallel ports. Check I/O cards.

FDC Check

Test floppy controller. Check the drive as well.

Count Shadow RAM

Run a series of memory tests on the system. Check for bad memory chips address lines or data lines.

Display Total Mem/Return to Real Mode

Total memory detected is displayed and the machine is returned to real mode. Check the keyboard controller or A20 line.

Back to Real Mode

Transition is attempted through the A20 line and the keyboard controller.

Check HDC

The hard drive controller is tested.

Check FDD

Attempts are made to initialise the floppy drives.

Turn off Gate A20 and Test CoProcessor

Attempts are made to transition back to real mode by disabling the A20 line then the coprocessor is tested if present. Check the keyboard controller coprocessor or improper setup in CMOS.

Set Time and Date

Time and date will be read from the RTC.

DTK POST Codes

Code

Meaning

01

Power on start

03

Initialise interrupt controller?a8259

05

Initialise video card?aMCA and CGA

0D

Initialise DMA controller?a8237

0E

Initialise page register?a74612

12

Test keyboard controller?a8042

16

Initialise DMA controller and timer

22

DRAM refresh testing

25

Base 64K memory testing

30

Set system stack

33

Read system configuration through 8042

37

Test keyboard clock and data line

40

Determine video type

44

Testing MGA and CGA if existing

48

Video 80 x 25 mode initialisation

4D

Display DTK BIOS title

4F

Check RS232 and printer

50

FDC check

55

Count shadow RAM

58

Display total memory and return to real mode

5A

Back to real mode

60

Check HDC

62

Check FDD

65

Check HDC

67

Initialise FDC and HDC

6A

Turn off gate A20 and test coprocessor

70

Set time and date according to RTC

77

Boot

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