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BIOS PostCodes

Intel Motherboards:

Intel RC440BX Motherboard:

Uncompressed INIT Code Checkpoints:

D0 NMI is Disabled. Onboard KBC, RTC enabled (if present). Init code Checksum verification starting
D1 Keyboard controller BAT test, CPU ID saved, and going to 4GB flat mode.
D3 Do necessary chipset initialization, start memory refresh, do Memory sizing.
D4 Verify base memory.
D5 Init code to be copied to segment 0 and control to be transferred to segment 0.
D6 Control is in segment 0. To check recovery mode and verify main BIOS checksum. If either it is recovery mode or main BIOS checksum is bad, go to check point E0 for recovery else go to check point D7 for giving control to main BIOS.
D7 Find main BIOS module in ROM image
D8 Uncompress the main BIOS module.
D9 Copy main BIOS image to F000 shadow RAM and give control to main BIOS in F000 shadow RAM.

Boot Block Recovery Code Check Points:

E0 Onboard Floppy Controller (if any) is initialized. Compressed recovery code is uncompressed in F000:0000 in Shadow RAM and give control to recovery code in F000 Shadow RAM. Initialize interrupt vector tables, initialize system timer, initialize DMA controller, interrupt controller.
E8 Initialize extra (Intel Recovery) Module.
E9 Initialize floppy drive
EA Try to boot from floppy. If reading of boot sector is successful, give control to boot sector code.
EB Booting from floppy failed, look for ATAPI (LS120, Zip) devices.
EC Try to boot from ATAPI. If reading of boot sector is successful, give control to boot sector code.
EF Booting from floppy and ATAPI device failed. Give two beeps. Retry the booting procedure again (go to check point E9).

Runtime Code Uncompressed in F000 Shadow RAM:

03 NMI is disabled. The check soft reset/power-on
05 BIOS stack set. Going to disable cache if any
06 POST code to be uncompressed
07 CPU Init and CPU data area Init to be done
08 CMOS checksum calculation to be done next
0B Any initialization before keyboard BAT to be done
0C KB controller I/B free. To issue the BAT command to keyboard controller
0E Any initialization after KB controller BAT to be done next
0F Keyboard command byte to be written
10 Going to issue Pin 23, 24 blocking/unblocking command
11 Going to check pressing of (INS>, <END> key during power on
12 To Init CMOS if "Init CMOS in every boot" is set or <END> key is pressed. Going to disable DMA and Interrupt controllers
13 Video display is disabled and port-B is initialized. Chipset init about to begin
14 8254 timer test about to start
19 About to start memory refresh test
1A Memory refresh line is toggling. Going to check 15µs ON/OFF time
23 To read 8042 input port and disable Megakey GreenPC feature. Make BIOS code segment writeable
24 To do any setup before Int vector init
25 Interrupt vector initialization to begin. To clear password if necessary
27 Any initialization before setting video mode to be done
28 Going for monochrome mode and color mode setting
2A Different buses init (system, static, output devices) to start if present
2B To give control for any setup required before optional video ROM check
2C To look for optional video ROM and give control
2D To give control to any processing after video ROM returns control
2E If EGA/VGA not found then do display memory R/W test
2F EGA/VGA not found. Display memory R/W test about to begin
30 Display memory R/W test passed. About to look for the retrace checking
31 Display memory R/W test and retrace checking failed. To do alternate Display memory R/W test
32 Alternate Display memory R/W test passed. To look for the alternate display retrace checking
34 Video display checking over. Display mode to be set next
37 Display mode set. Going to display the power on message
38 Different buses init (input, IPL, general devices) to start if present
39 Display different buses initialization error messages
3A New cursor position read and saved. To display the hit <DEL> message
40 To prepare the descriptor tables
42 To enter in virtual mode for memory test
43 To enable interrupts for diagnostic mode
44 To initialize data to check memory wrap around at 0:0
45 Data initialized. Going to check for memory wrap around at 0:0 and finding the total system memory size
46 Memory wrap around test done. Memory size calculation over. About to go for writing patterns to teat memory
47 Pattern to be tested written in extended memory. Going to write patterns in base 540K memory
48 Patterns written in base memory. Going to find out amount of memory below 1MB memory
49 Amount of memory below 1MB found and verified. Going to find out amount of memory above 1MB memory
4B Amount of memory above 1MB found and verified. Check for soft reset and going to clear memory below 1MB for soft reset
4C Memory below 1MB cleared. Going to clear memory above 1MB
4D Memory above 1MB cleared. Going to save the memory size
4E Memory test started. About to display the first 64K memory size
4F Memory size display started. This will be updated during the memory test. Going for sequential and random memory test
50 Memory testing/initialization below 1MB complete. Going to adjust displayed memory size for reallocation/shadow
51 Memory size display adjusted due to reallocation/shadow. Memory test above 1MB to follow
52 Memory testing/initialization above 1MB complete. Going to save memory size information
53 Memory size information is saved. CPU registers are saved. Going to enter real mode
54 Shutdown successful, CPU in real mode. Going to disable gate A20 line and disable parity/NMI
57 A20 address line, parity/NMI disable successful. Going to adjust memory size depending on reallocation/shadow
58 Memory size adjusted for reallocation/shadow. Going to clear Hit <DEL> message
59 Hit <DEL> message cleared. <WAIT...> message displayed. About to start DMA and interrupt controller test
60 DMA page register test passed. To do DMA #1 base register test
62 DMA #1 base register test passed. To do DMA #2 base register test
65 DMA #2 base register test passed. To program DMA unit 1 and 2
66 DMA unit 1 and 2 programming over. To initialize 8259 interrupt controller
7F Extended NMI( sources enabling is in progress
80 Keyboard test started. Clearing output buffer, checking for stuck key, to issue keyboard reset command.
81 Keyboard reset error/stuck key found. To issue keyboard controller interface test command
82 Keyboard controller interface test over. To write command byte and init circular buffer
83 Command byte written, global data init done. To check for lock-key
84 Lock-key checking over. To check for memory size mismatch with CMOS
85 Memory size check done. To display soft error and check for password or bypass setup
86 Password checked. About to do programming before setup
87 Programming before setup complete. To uncompress SETUP code and execute CMOS setup
88 Returned from CMOS setup program and screen is cleared. About to do programming after setup
89 Programming after setup complete. Going to display power on screen message
8B First screen message displayed. <WAIT..> message displayed. PS/2 mouse check and extended BIOS data area allocation to be done
8C Setup options programming after CMOS setup about to start
8D Going for hard disk controller reset
8F Hard disk controller reset done. Floppy setup to be done next
91 Floppy setup complete. Hard disk setup to be done next
95 Init of different buses optional ROMs from C800 to start
96 Going to do any init before C800 optional ROM control
97 Any init before C800 optional ROM control is over. Optional ROM check and control will be done next
98 Optional ROM control is done. About to give control to do any required processing after optional ROM returns control and enable external cache
99 Any initialization required after optional ROM test over. Going to setup timer data area and printer base address
9A Return after setting timer and printer base address. Going to set the RS-232 base address
9B Returned after RS-232 base address. Going to do any initialization before coprocessor test
9C Required initialization before coprocessor is over. Going to initialize the coprocessor next
9D Coprocessor initialized. Going to do any initialization after coprocessor test
9E Initialization after coprocessor test is complete. Going to check extended keyboard, keyboard ID and num-lock
A2 Going to display and soft errors
A3 Soft error display complete. Going to set keyboard typmatic rate
A4 Keyboard typmatic rate set. To program memory wait states
A7 NMI and parity enabled. Going to do any initialization required before giving control to optional ROM at E000
A8 Initialization before E000 ROM control over. E000 ROM to get control next
A9 Returned from E000 ROM control. Going to do any initialization required after E000 optional ROM control
AA Initialization after E000 optional ROM control is over. Going to display the system configuration
AB Put INT13 module runtime image to shadow
AC Generate MP for multiprocessor support (if present)
AD Put CGA INT10 module (if present) in shadow
AE Uncompress SMBIOS module and init SMBIOS code and form the runtime SMBIOS image in shadow
B1 Going to copy any code to specific area
00 Copying of code to specific area done. Going to give control to INT19 boot loader

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