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"The computer book of the month is The Bios Companion by Phil Croucher. Long-time readers of this column will recall I have recommended his book before. This tells you everything you ought to know about the BIOS in your system. Post codes, options, upgrades, you name it.

Years ago, I called an earlier edition of this invaluable and I see no reason to change my view. Recommended.
"

Jerry Pournelle
Byte Magazine

"Croucher's book was invaluable 20 years ago and remains so today...... Every one of the 468 pages holds useful information, the author having zero tolerance for padding."

Davey Winder
PC Plus Magazine

"You've completerly impressed me with the quality and scope of your guides - extreme care has obviously gone into their research and preparation."

Jeremy Fleming

"His style is lovely: clear, jargon-free where possible, chatty and friendly with beautiful short paragraphs. It [Communications & Networks] joins my list of 'I wish I'd written it' books. I haven't come across such a good subject book in a long time at this price."

Lorna Kyle
Personal Computer World

"To any micro owner who wants to know what this comms business is all about, [Communications & Networks] is certainly one of the best around. ... Croucher is not only knowledgable about his subject, he's interested in it and communicates that interest to you. "

Ron Peck
New Computer Express

"There are few books about which explain as accurately and comprehensively as [Communications & Networks] does what communications are all about. The glossary is excellent."

Micro Decision

"...any PC user with a genuine interest in using his machine to its full potential will recognise [Communications & Networks] for the completely invaluable tool and often the inspiration that it is."

Yvonne Taylor
Which PC

"[Communications & Networks] is the type of book you can read on a bus or train without getting a headache from trying to understand what it means."

Network

"As a recently reformed computer illiterate myself, I appreciated the author's straighforward yet humourous and light-hearted style of writing. He manages to strike the balance between too much and too little information. ... [Computing Under Protest] is never in danger of either boring or confusing the reader."

Emma Tyrrall
Practical PC

"Good documentation is important for any software, but even more so for an operating system - the documentation [for DOS 386 Professional] has some exceptionally clear explanations. Altogether, the documentation is an example of the right way of doing things, and other software manufacturers would do well to take note."

Matthew Holbrook
Computer Shopper

"The DOS 386 Professional manual sets arrived at 2130 local time today. We have had a brief look at them and wish to congratulate IMS on the excellent, clear and concise manner in which they have been presented."

Fred Parker
ETL Soft

"I remain impressed by Mr. Croucher's fluid writing style, practical orientation, enthusiasm, and strong technical knowledge."

Lance A Leventhal
Slawson Communications, Inc



JAR Professional Pilot Studies

"Its real value lies in taking the plethora of booklets and ring-bound photocopies associated with commercial examinations and condensing them into an attractive and portable form. The guy really does deserve a medal ~ he has made a genuine contribution to the body of professional aviation literature assembled during the course of the last century.

I heartily recommend it to students of commercial flight, if only as a souvenir of their efforts... "

Colin Hilton
Pro Pilot's Rumour Network

"(The) Book is quite a good compliment to our notes for students. We will be recommending all our students buy the books.... "

Chris
Naples Air Centre

"I got your book last month and am in the process of ploughing through it! Actually, I really like it and find it very interesting and easy to read."

Simon Rouse

"So far I have found your book an extremely helpful reference manual to carry around in my flight bag."

Blair Clubley

"I wish to commend you on a "work of art". I wish the CAA would produce a quick reference easy to read manual such as yours. Truly wonderful!"

Ebrahim Parkar

 
Post Codes
 Acer
 ALR

 AMI
 Arche
 AST
 AT&T
 Award
 Chips & Technologies
 Compaq
 Dell
 DTK
 Eurosoft/Mylex
 Faraday A-Tease
 HP
 IBM
 Intel
 Landmark
 Microid/MR
 NCR
 Olivetti
 Philips
 Phoenix
 Quadtel
 Supersoft
 Tandon
 Zenith

HP POST Codes

Derived from Phoenix, all POST information is sent to the screen.

Note: Not all POST codes are included below - the latest information is in the The BIOS Companion, which contains over 100 pages of them.


POST Procedures

CPU Registers in CPU tested with data patterns, error flags are set, verified and reset
ROM BIOS Checksum Checksums are performed on high and low BIOS chips
PIC Test Test timer channels 0-2 then the memory refresh signal.  Initialize timer if tests are passed.  Check the 8254 chip
64K Test Walking bit and address collision tests are performed on the first 64K of memory.  Check for a bad memory chip or address line
Cache Controller The the CPU cache controller and memory
Video Adapter Initialize the video adapter.  If EGA.VGA is present, wait for the adapter to finish internal diagnostics.  Check for adapter or improper setup if a failure occurs
DMA Test Bit patterns written to all DMA controller registers, including page registers, and verifies the patterns written.   If the tests pass the registers are reset and the controller initialized
PIC Test Test mask register of master and slave interrupt controllers.  Generate interrupt and monitor CPU to test success.   Failure is normally down to the PIC but the interrupt test uses the BIOS clock (interrupt) and the RTC, so check those also
Keyboard Controller Perform several tests on the 8042 keyboard controller then send a series of interrupt request commands via the 8259 PIC
HP-HIL Test Test the HP-HIL (Hardware Interrupt Level) controller with data patterns and verify it
CMOS Test Perform a checksum on the standard and extended CMOS RAM area.  Perform a register test and check byte 0D  to determine power status.  Check the CMOS extended CMOS RAM or battery respectively if a failure occurs
Manufacturing Loop Search for diagnostic tool used in manufacturing and run predetermined tests if found.  Otherwise continue POST
Base Memory Test Test RAM between 64K and 640K with several pattern test.  The bit failure and bank can be determined by the displayed hex code
Extended Memory Test Test extended memory found.  Bank and failing bit displayed by the hex code
RTC Test Test the RTC portion of the CMOS chip
Keyboard Controller Test keyboard controller.   Initialize keyboard if no errors found
Floppy Disk Test and initialize floppy controllers and drives found.  Check specific errors with the displayed hex code.  Check for correct setup or defective CMOS chip or defective battery
Math Coprocessor Test NPU registers and interrupt request functions
CPU Clock Test Test interface between CPU and system at different speeds.  Check for incorrect clock setting for system peripherals or a bad CPU or clock generator chip
Serial and Parallel Test Test and initialize serial and parallel ports.  Failure here will not halt the POST.  The Vectra RS BIOS does not test the parallel port
Boot Initialize the BIOS vector table, standard and extended CMOS data areas and any adapter ROM's present.  Then call Int 19 boot loader and give control to it.  Failures past this point usually point to the hard drive or corrupt bootloader code

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Vectra

A failure during POST will emit four beeps, and a 4-digit hex code to the monitor. Failures that occur before EGA/VGA monitors are initialised will not be displayed, so use a mono instead. BIOSes prior to March 1989 initialised the video before getting on with the POST.

01 LED test
02 Processor test
03 System (BIOS) ROM test
04 RAM refresh timer test
05 Interrupt RAM test
06 Shadow the system ROM BIOS
07 CMOS RAM test
08 Internal cache memory test
09 Initialize the video card
10 Test external cache
11 Shadow option ROM's
12 Memory subsystem test
13 Initialize EISA/ISA hardware
14 8042 keyboard controller self test
15 Timer 0 / Timer 2 test
16 DMA subsystem test
17 Interrupt controller test
18 RAM address line independence test
19 Size extended memory
20 Real mode memory test (first 640K)
21 Shadow RAM test
22 Protected mode RAM test (extended RAM)
23 Real time clock test
24 Keyboard test
25 Mouse test
26 Hard disk test
27 LAN test
28 Flexible disk controller subsystem test
29 Internal numeric coprocessor test
30 Weitek coprocessor test
31 Clock speed switching test
32 Serial port test
33 Parallel port test

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Vectra ES

 

000F 80286 CPU is bad
0010 Bad checksum on ROM 0
0011 Bad checksum on ROM 1
011X One of the RTC registers is bad; Register = x(0-D)
0120 RTC failed to tick
0240 CMOS/RTC has lost power
0241 Invalid checksum, IBM CMOS area
0280 Invalid checksum, HP CMOS area
02XY One of the CMOS registers is bad; Register = XY - 40
0301 8042 failed to accept the reset command
0302 8042 failed to respond to the reset command
0303 8042 failed to reset
0311 8042 failed to accept the "WRITE CMD BYTE" command
0312 8042 failed to accept the data of the above command
0321 8042 failed to accept scancode from port 68
0322 8042 failed to respond to the above scancode
0323 8042 responded incorrectly to the above scancode
0331 8042 failed to accept command from port 6A
0332 8042 failed to generate SVC on port 67
0333 8042 generated HPINT type on port 65
0334 8042 failed the R/W register on port 69
0335 8042 failed to generate HPINT on IRQ 15
0336 8042 failed to generate HPINT on IRQ 12
0337 8042 failed to generate HPINT on IRQ 11
0338 8042 failed to generate HPINT on IRQ 10
0339 8042 failed to generate HPINT on IRQ 7
033A 8042 failed to generate HPINT on IRQ 5
033B 8042 failed to generate HPINT on IRQ 4
033C 8042 failed to generate HPINT on IRQ 3
0341 8042 failed keyboard interface test command
0342 8042didn't respond to interface command
0343 Keyboard clock line stuck low
0344 Keyboard clock line stuck high
0345 Keyboard data line stuck low
0346 Keyboard data line stuck high
0350 No ACK from keyboard self test command
0351 Bad ACK from keyboard self test command
0352 Keyboard is dead or not connected
0353 No result from keyboard self test command
0354 Keyboard self test failed
0401 8042 failed to enable gate A-20
0503 Serial port dead or non existent
0505 Serial port fails port register tests
0543 Parallel port dead or non-existent
06XX Stuck key; XX=scancode of key
0700 Failed to switch to slow mode
0701 Failed to switch to dynamic mode
0702 Timer (channel 0) failed to interrupt
0703 Memory cycles too slow in slow mode
0704 Memory cycles too fast in slow mode
0705 I/O cycles too slow in slow mode
0706 I/O cycles too fast in slow mode
0707 Memory cycles too slow in dynamic mode
0708 Memory cycles too fast in dynamic mode
0709 I/O cycles too slow in dynamic mode
070A I/O cycles too fast in dynamic mode
110X One of the timer channels failed to register test / X(0-2)=channel that failed
1200 Memory refresh signal stuck high
1201 Memory refresh signal stuck low
211X DMA 1 failed R/W test at register x (0-7)
212X DMA 2 failed R/W test at register x (0-7)
221X Bad DMA page register; X=register 0-7
300X HP-HIL controller failed self test; X=data
  X = xx1 = >read/write fail with data = 0DA5h
  X = xx1x = >read/write fail with data = 0DA5h
  X = x1xx = >read/write fail with data = 0DA5h
  X = 1xxx = >read/write fail with data = 0DA5h
3010 HP-HIL device test failed
4XYZ Lower 640K failed R/W test;
  X=0,2,4,6   Y>0=Bad U23     Z>0=Bad U13
  X=1,3,5,7   Y>0=Bad U43     Z>0=Bad U33
  X=8          Y>0=Bad U22     Z>0=Bad U12
  X=9          Y>0=Bad U42     Z>0=Bad U32
5XYZ Lower 640K failed marching ones test
  X = bbbx = > bbb (0-7) is # of 128K bank
  bbb0 = > Indicate even byte bad
  bbb1 = > Indicate odd byte bad
  YZ = bbbb bbbb = > Bits for which b = 1 are bad
61XY RAM address line XY stuck
  Some address lines to RAM are stuck to 0 or 1
  XY = 00bb bbbb = > RAM address line bbbbbb is stuck
  XY = 01bb bbbb = > Multiple address lines are stuck (bbbbbb is the first bad one)
620X Lower 640K parity error; Bank X
  X = Address in 64K bank where parity error occurred
  if X = 0 to y, U21 and/or U31 is/are bad
  if X = 8 to 9, U11 and/ore U41 is/are bad
63XY Parity error above 1MB; Bank XY
  Parity error has occurred during RAM test above the first MB
  XY = Address in 64K bank where parity occurred
6400 Parity generator failed to detect error
71XY Master 8259 failed R/W; bits XY
  XY = bbbb bbbb + > bits in which b = 1 is bad
72XY Slave 8259 failed R/W; bits XY
  XY = bbbb bbbb = > bits in which b = 1 is bad
7400 Master 8259 failed interrupt
7500 Slave 8259 failed interrupt
9XYZ Floppy drive controller error
  X=drive #
  Y=0=1st level error
      Z=0   Unsuccessful input from FD
      Z=1   Unsuccessful output to FDC
      Z=2  Error while executing seek
      Z=3  Error during recalibrate
      Z=4  Error verifying RAM buffer
      Z=5  Error while resetting FDC
      Z=6  Wrong drive identified
      Z=7  Wrong media identified
      Z=8  No interrupt from FDC
      Z=9  Failed to detect track 0
      Z=A  Failed to detect index pulse
  Y>1=Higher level error
  Y=1=Read sector error, side 0
  Y=2=Read sector error, side 1
  Y=3=Write sector error, side 0
  Y=4=Write sector error, side 1
  Y=5=Format sector error, side 0
  Y=6=Format sector error, side 1
  Y=7=Read ID error, side 0
  Y=8=Read ID error, side 1
      Z=1=No ID address mark
      Z=2=No data address mark
      Z=3=Media is write protected
      Z=4=Sector # wrong
      Z=5=Cylinder # wrong
      Z=6=Bad cylinder
      Z=7=DMA overrun
      Z=8=ID CRC error
      Z=9=Data CRC error
      Z=A=End of cylinder
      Z=B=Unrecognizable error
A001 No 80287 detected
A002 80287 failed stack register R/W test
A00C No zero-divide interrupt from 80287
CXYZ R/W error on extended RAM in XY bank
  Read/Write test failure on extended RAM
  X = 0 = > Even byte is bad
  X = 1 = > Odd byte is bad
  XY = Address in 64K bank where RAM failed
CFFF Extended RAM marching ones failed
  Marching on test failure on extended RAM
  X = 0 = > Even byte bad
  X = 1 = > Odd byte bad
  XA = Address in 64K bank where RAM failed

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Vectra QS & RS

 

000F 386 CPU bad
0010 Bad checksum on ROM 0
0011 Bad checksum on ROM 1
011X RTC register is bad
0120 RTC failed to tick
0240 CMOS/RTC lost power
0241 Invalid checksum, IBM CMOS area
0280 Invalid checksum, HP CMOS area
02XY Bad CMOS register, at XY-40
0301 8042 failed to accept reset command
0302 8042 failed to respond to reset
0303 8042 failed on reset
0311 8042 didn't accept "WRITE CMD BYTE"
0312 8042 didn't accept data
0321 8042 failed to accept scancode, port 68
0322 8042 failed to respond to the above scancode
0323 8042 responded incorrectly to the above scancode
0331 8042 failed to accept command from port 6A
0332 8042 failed to generate SVC on port 67
0333 8042 generated HPINT type on port 65
0334 8042 failed the R/W register on port 69
0335 8042 failed to generate HPINT on IRQ 15
0336 8042 failed to generate HPINT on IRQ 12
0337 8042 failed to generate HPINT on IRQ 11
0338 8042 failed to generate HPINT on IRQ 10
0339 8042 failed to generate HPINT on IRQ 7
033A 8042 failed to generate HPINT on IRQ 5
033B 8042 failed to generate HPINT on IRQ 4
033C 8042 failed to generate HPINT on IRQ 3
0341 8042 failed keyboard interface test command
0342 8042didn't respond to interface command
0343 Keyboard clock line stuck low
0344 Keyboard clock line stuck high
0345 Keyboard data line stuck low
0346 Keyboard data line stuck high
0350 No ACK from keyboard self test command
0351 Bad ACK from keyboard self test command
0352 Keyboard is dead or not connected
0353 No result from keyboard self test command
0354 Keyboard self test failed
0401 8042 failed to enable gate A-20
0503 Serial port dead or non-existent
0505 Serial port fails port register tests
06XX Stuck key; XX=scancode of key
0700 Failed to switch to slow speed
0701 Failed to switch to fast speed
0702 Timer failed to interrupt
0703 CPU clock too slow in slow speed
0704 CPU clock too fast in slow speed
0707 CPU clock too slow in fast speed
0708 CPU clock too fast in fast speed
0709 Failed to switch bus clock to ATCLK
110X Timer X (0-2) failed to register test
1200 Memory refresh signal stuck high
1201 Memory refresh signal stuck low
211X DMA 1 failed R/W test at register x (0-7)
212X DMA 2 failed R/W test at register x (0-7)
221X Bad DMA page register; X=register 0-7
300X HP-HIL controller failed self test; X=data
  X = xxx1 = > read/write fail with data = 0DA5Ah
  X = xx1x = > read/write fail with data = 0DA5Ah
  X = x1xx = > read/write fail with data = 0DA5Ah
  X = 1xxx = > read/write fail with data = 0DA5Ah
3010 HP-HIL device test failed
4XYZ Lower 640K failed R/W test;
  X=0,2,4,6   Y>0=Bad U23     Z>0=Bad U13
  X=1,3,5,7   Y>0=Bad U43     Z>0=Bad U33
  X=8          Y>0=Bad U22     Z>0=Bad U12
  X=9          Y>0=Bad U42     Z>0=Bad U32
5XYZ Lower 640K failed marching ones test
  RAM in lower 640K failed read/write test
  X = bbcc = > bb is # 64K of 32 bit word bank
  cc = 00 = > byte 0 is bad
  cc = 01 = > byte 1 is bad
  cc = 02 = > byte 2 is bad
  cc = 03 = > byte 3 is bad
  YZ = bbbb bbbb = > bits for which b = 1 are bad
61XY RAM address line XY stuck
  Some address lines to RAM are stuck to 0 or 1
  XY = 00bb bbbb = > RAM address line bbbbbb is stuck
  XY = 01bb bbbb = > Multiple address lines are stuck bbbbbb is the first bad one
620X Lower 640K parity error; Bank X
  X = Address in 64K bank where parity occurred
63XY Parity error above 1MB; Bank XY
  XY = Address in 64K bank where parity occurred
6500 Shadow RAM bad at BIOS segment
6510 Shadow RAM bad at HP EGA segment
71XY Master 8259 failed R/W; bits XY
  XY = bbbb bbbb = > bits which b = 1 is bad
72XY Slave 8259 failed R/W; bits XY
  XY = bbbb bbbb = > bits which b = 1 is bad
7400 Master 8259 failed interrupt
7500 Slave 8259 failed interrupt
9XYZ Floppy drive controller error
  X=drive #
  Y=0=1st level error
      Z=0   Unsuccessful input from FD
      Z=1   Unsuccessful output to FDC
      Z=2  Error while executing seek
      Z=3  Error during recalibrate
      Z=4  Error verifying RAM buffer
      Z=5  Error while resetting FDC
      Z=6  Wrong drive identified
      Z=7  Wrong media identified
      Z=8  No interrupt from FDC
      Z=9  Failed to detect track 0
      Z=A  Failed to detect index pulse
  Y>1=Higher level error
  Y=1=Read sector error, side 0
  Y=2=Read sector error, side 1
  Y=3=Write sector error, side 0
  Y=4=Write sector error, side 1
  Y=5=Format sector error, side 0
  Y=6=Format sector error, side 1
  Y=7=Read ID error, side 0
  Y=8=Read ID error, side 1
      Z=1=No ID address mark
      Z=2=No data address mark
      Z=3=Media is write protected
      Z=4=Sector # wrong
      Z=5=Cylinder # wrong
      Z=6=Bad cylinder
      Z=7=DMA overrun
      Z=8=ID CRC error
      Z=9=Data CRC error
      Z=A=End of cylinder
      Z=B=Unrecognizable error
A001 No 80287 detected
A002 80287 failed stack register R/W test
A00C No zero-divide interrupt from 80287
AF00 Weitek coprocessor didn't enter protected mode
AF01 Weitek coprocessor nor present
AF02 Weitek coprocessor fails register test
AF05 Weitek coprocessor fails addition test
AF06 Weitek coprocessor fails interrupt test
AF0C Weitek coprocessor fails interrupt test
CXYZ R/W error on extended RAM in XY bank
  X = 0 = > Even byte bad
  X = 1 = > Odd byte bad
  XY = Address in 64K bank where RAM failed
CFFF No extended RAM found
EXYZ Extended RAM marching ones failure at XYZ
  X = 0 = > Byte 0 is bad
  X = 1 = > Byte 1 is bad
  X = 2 = > Byte 2 is bad
  X = 3 = > Byte 3 is bad

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Pavilion 3100 & 8000

 

02 Verify real mode
03 Disable NMI
04 Get processor type
06 Initialize system hardware
08 Initialize chipset with POST values
09 Set IN-POST flags
0A Initialize CPU registers
0B Enable CPU registers
0C Initialize cache to POST values
0E Initialize I/O component
0F Initialize local IDE bus
10 Initialize power management
11 Load alternate registers
12 Restore CPU control word during warm boot
13 Initialize PCI bus mastering devices
14 Initialize keyboard controller
16 BIOS ROM checksum
17 Initialize cache before memory size
18 Initialize 8254 timer
1A Initialize DMA controller
1C Reset PIC
20 Test DRAM refresh
22 Test 8742 keyboard controller
24 Set ES segment register to 4GB
26 Enable A-20 line
28 Autosize DRAM
29 Initialize POST memory manager
2A Clear 512K base RAM
2C RAM address line failure
2E RAM data failure, low byte
2F Enable cache before BIOS shadow
30 RAM data failure, high byte
32 Test CPU, BUS clock frequency
33 Initialize POST dispatch manager
34 Test CMOS RAM
35 Initialize alternate chipset registers
36 Warm start shut-down
37 Reinitialize chipset (MB only)
38 Shadow system BIOS ROM
39 Reinitialize cache (MB only)
3A Autosize cache
3C Configure advanced chipset registers
3D Load alternate registers new CMOS values
40 Set initial CPU speed
42 Initialize interrupts
44 Initialize BIOS interrupts
45 POST device initialization
46 Check ROM copyright notice
47 Initialize manager for PCI option ROM's
48 Check video config against CMOS
49 Initialize manager for PCI option ROM's
4A Initialize all video adapters
4B Display quiet boot screen
4C Shadow video BIOS
4E Display BIOS copyright notice
50 Display CPU type & speed
51 Initialize
52 Test keyboard
54 Set key click if enabled
56 Enable keyboard
58 Test for unexpected interrupts
59 Initialize POST display service
5A Display "Press F2 to Enter Setup"
5B Disable CPU cache
5C Test RAM, 512-640K
60 Test extended memory
62 Test extended memory address lines
64 Jump to user patch 1
66 Configure advanced cache registers
67 Initialize multi-processor APIC
68 Enable external & processor caches
69 Set up SMM area
6A Display external L2 cache size
6C Display shadow area message
6E Display high address for UMB recovery
70 Display error message
72 Check for configuration errors
74 Test real time clock
76 Check for keyboard errors
7A Test for key lock on
7C Set up hardware interrupt vectors
7E Initialize coprocessor, if present
80 Disable onboard super I/O ports
81 Late POST device initialization
82 Detect & install external RS-232 ports
83 Configure non-MDC IDE controllers
84 Detect & install external parallel ports
85 Initialize PnP ISA devices
86 Reinitialize onboard I/O ports
87 Configure motherboard configurable devices
88 Initialize BIOS data area
89 Enable NMI's
8A Initialize extended BIOS data area
8B Test & initialize PS/2 mouse
8C Initialize floppy controller
8F Determine number of ATA drives
90 Initialize hard disk controllers
91 Initialize local BUS HD controllers
92 Jump to user patch 2
93 Build MPTABLE for multiprocessor boards
94 Disable A-20 line
95 Install CD-ROM for boot
96 Clear huge ES segment register
97 Fix up multiprocessor table
98 Search for options ROM's
99 Check for smart drive
9A Shadow ROM option
9C Set up power management
9E Enable hardware interrupts
9F Determine number of ATA & SCSI drives
A0 Set time of day
A2 Check key lock
A4 Initialize typematic rate
A8 Erase F2 prompt
AA Scan for F2 keystroke
AC Enter SETUP
AE Clear IN-POST flag
B0 Check for errors
B2 POST done, prepare for boot
B4 One short beep before boot
B5 Terminate quiet boot
B6 Check password (optional)
B8 Clear global descriptor table
B9 Clean up all graphics
BA Initialize DMI parameters
BB Initialize PnP option ROM's
BC Clear parity checkers
BD Display multi boot menu
BE Clear screen optional
BF Check virus and backup reminders
C0 Try to boot with Int 19
C1 Initialize POST error manager
C2 Initialize error logging
C3 Initialize error display function
C4 Initialize system error handler
E0 Initialize the chipset
E1 Initialize the bridge
E2 Initialize the processor
E3 Initialize system timer
E4 Initialize system I/O
E5 Check force recovery boot
E6 Checksum BIOS ROM
E7 Got to BIOS
E8 Set huge segment
E9 Initialize multiprocessor
EA Initialize OEM special code
EB Initialize PIC & DMA
EC Initialize memory type
ED Initialize memory type
EE Shadow boot block
EF System memory test
F0 Initialize interrupt vectors
F1 Initialize runtime clock
F2 Initialize video
F3 Initialize beeper
F4 Initialize BOOT
F5 Clear huge segment
F6 Boot to mini-DOS
F7 Boot to full DOS

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