"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."


"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.... "

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."

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

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"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

 Chips & Technologies
 Faraday A-Tease

Compaq POST Codes

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

General Codes


00 Initialize flags, MSW,IDTLIN
01 Read manufacturing jumper
02 8042 received read command
03 No response from 8042
04 Look for ROM at E000
05 Look for ROM at C800
06 Normal CMOS reset code
08 Initialize 8259,80287
09 Reset code in CMOS byte
0A Vector vis 40:67 reset function
0B Vector vis 40:67 with E01 function
0C Boot reset function
0D Test #2 8254 PIT counter 0
0E Test #2 8254 PIT counter 2
0F Warm boot
10 PPI disabled, test 8254 PIT's 0 and 1
11 Initialize (blast) VDU controller
12 Clear screen; turn ON video
13 Test time 0
14 Disable RTC interrupts
15 Check battery power
16 Battery has lost power
17 Clear CMOS Diags.
18 Test base memory (First 128K)
19 Initialize base memory
1A Initialize VDU adapters
1B The system ROM
1C CMOS checksum
1D DMA controller/page registers
1E Test keyboard controller
1F Test 286 protected mode
20 Test real and extended memory
21 Initialize time-of-day
22 Initialize 287 coprocessor
23 Test the keyboard and 8042
24 Reset A20, set default CPU speed
25 Test diskette subsystem
26 Test fixed disk subsystem
27 Initialize parallel printer
28 Perform search for optional ROM's
29 Test valid system configuration
2A Clear screen
2B Check for invalid time and date
2C Optional ROM search
2D Test timer 2
2F Write to diagnostic byte
30 Clear first 128K bytes of RAM
31 Load interrupt vectors 70-77
32 Load interrupt vectors 00-1F
33 Initialize MEMSIZE and RESETWD
34 Verify CMOS checksum
35 CMOS checksum is not valid
36 Check battery power
37 Check for game adapters
38 Check for Serial ports
39 Check for parallel printer ports
3A Initialize port and comm time-outs
3B Flush keyboard buffer
40 Save RESETWD value
41 Check RAM refresh
42 Start write of 128K RAM test
43 Reset parity checks
44 Start verify of 128K RAM test
45 Check for parity errors
46 NO RAM errors
47 RAM error detected
50 Check for dual frequency in CMOS
51 Check CMOS VDU configuration
52 Start VDU ROM search
53 Vector to VDU option ROM's
54 Initialize first display adapter
55 Initialize second display adapter
56 No display adapters installed
57 Initialize primary VDU mode
58 Start of VDU test (each adapter)
59 Check existence of adapter
5A Check VDU registers
5B Start screen memory test
5C End test of adapter, clear memory
5D Error detected on an adapter
5E Test the next adapter
5F All adapters successfully tested
60 Start of memory tests
61 Enter protected mode
62 Start memory sizing
63 Get CMOS size
64 Start test of real memory
65 Start test of extended memory
66 Save size memory (base, ext)
67 128K-option installed CMOS bit
68 Prepare to return to real mode
69 Back in real mode-successful
6A Protected mode error during test
6B Display error message
6C End of memory test
6D Initialize KB OK string
6E Determine size to test
70 Display XXXXXKB OK
71 Test each RAM segment
72 High order address test
74 Parity error on bus
75 Start protected mode test
76 Prepare to enter protected mode
77 Test software exceptions
78 Prepare to return to real mode
79 Back in real mode-successful
7A Back in real mode-error occurred
7B Exit protected mode
7C High order address test failure
7D Entered cache controller test
7E Programming memory cache
7F Copy system ROM to high RAM
80 Start of 8042 test
81 Do 8042 self test
82 Check result received
83 Error result
84 OK 8042, Init mode=5D
86 Start test, reset keyboard
87 Got acknowledge, read result
88 Got result, check it
89 Test for stuck keys
8B Test keyboard interface
8A Key seems to be stuck
8C Got result, check it
8D End of test, no errors
90 Start of CMOS test
91 CMOS seems to be OK
92 Error on CMOS read,write test
93 Start of DMA controller test
94 Page registers seem to be OK
95 DMA controller is OK
96 8237 initialization is complete
97 Start of NCA RAM test
A0 Start of diskette tests
A1 FDC reset active (3F2h Bit 2)
A2 FDC reset inactive (3F2h Bit 2)
A3 FDC motor on
A4 FDC time-out error
A5 FDC failed reset
A6 FDC passed reset
A8 Start to determine drive type
A9 Seek operation initialized
AA Waiting for FDC seek status
AF Diskette tests complete
B0 Start of fixed drive tests
B1 Combo board not found-exit
B2 Combo controller failed-exit
B3 Testing drive 1
B4 Testing drive 2
B5 Drive error (error condition)
B6 Drive failed (failed to respond)
B7 No fixed drives-exit
B8 Fixed drive tests complete
B9 Attempt to boot diskette
BA Attempt to boot fixed drive
BB Boot attempt failed FD/HD
BC Jump to boot record
BD Drive error, retry booting
BE Weitek coprocessor test
D0 Entry to clear memory routine
D1 Ready to go to protected mode
D2 Ready to clear extended memory
D3 Ready to reset back to real mode
D4 Back in real mode
D5 Clear base memory
DD Built-in self-test failed
E0 Ready to replace E000 ROM
E1 Completed E000 ROM replacement
E2 Ready to replace EGA ROM
E3 Completes EGA ROM replacement

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Deskpro 286


01 Central processing unit
02 Coprocessor
02 Direct memory access
04 Interrupt controller
05 Port 61
06 Keyboard controller
10 Programmable timer
11 Refresh detect test
12 Speed test
14 Speaker test
21 Memory read/write
24 Memory address
25 Walking I/O
31 Keyboard short test
32 Keyboard long test
33 Keyboard LED test
35 Security lock test
41 Printer failed
42 Printer date, interrupt
43 Printer pattern test
48 Printer failed
51 VDU controller test
52 VDU controller test
53 VDU attribute test
54 VDU character set test
55 VDU 80 x 25 mode
56 VDU 80 x 25 mode
57 VDU 40 x 25 mode
60 Diskette drive ID test
61 Format
62 Read test
63 Write/read compare test
64 Random seek
65 ID media test
66 Speed test
67 Wrap test
68 Write protect test
69 Reset controller test

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Deskpro 386


01 I/O ROM error
02 System memory board failure
12 System option error
13 Time and date not set
14 Memory size error
21 Memory error
23 Memory address error
25 Memory error
26 Keyboard error
33 Keyboard controller error
34 Keyboard or system unit error
41 Printer error
42 Monochrome adapter failure
51 Display adapter failure
61 Diskette controller failure
62 Diskette boot recorder error
65 Ext. FDC failed got to internal F
6A Floppy port address conflict
6B Floppy port address conflict
72 Coprocessor detection

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Deskpro 486


01 CPU test failed
02 Coprocessor or Weitek error
03 DMA page registers
04 Interrupt controller master
05 Port 61 error
06 Keyboard controller self test
07 CMOS RAM test failed
08 CMOS interrupt test failed
09 CMOS clock load data test
10 Programmable timer
11 Refresh detect test failed
12 Speed test slow mode out of range
13 Protected mode test failed
14 Speaker test failed
16 Cache memory configuration
19 Installed devices test
21 Memory machine ID test failed
22 Memory system ROM checksum
23 Memory read/write test failed
24 Memory address test failed
25 Walking I/O test failed
26 Increment pattern test failed
31 Keyboard short test, 8042
32 Keyboard long test failed
33 Keyboard LED test, 8042
34 Keyboard typematic test failed
41 Printer failed or not connected
42 Printer data register failed
43 Printer pattern test
48 Printer not connected
51 Video controller test failed
52 Video memory test failed
53 Video attribute test failed
54 Video character set test failed
55 Video 80 x 25 mode
56 Video 80 x 25 mode
57 Video 40 x 25 mode test failed
58 Video 320 x 200 mode color set 1
59 Video 320 x 200 mode color set 1
60 Diskette ID drive types test
61 Diskette format failed
62 Diskette read test failed
63 Diskette write, read, random seek
65 Diskette media ID failed
66 Diskette speed test failed
67 Diskette wrap test failed
68 Diskette write protect test
69 Diskette reset controller test
82 Video memory test failed
84 Video adapter test failed

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Video BIOS

00 Entry into video ROM
01 Test alternate adapters
02 Perform vertical sync tests
03 Perform horizontal sync tests
04 Perform static system tests
05 Perform bug tests
06 Peform configuration tests
07 Perform alternate ROM tests
08 Run color gun off tests
09 Run color gun on tests
0A Test video memory
0B Check that adapter board is present
10 Error...illegal configuration
20 vertical sync present
21 Error...vertical sync out of range
30 horizontal sync present
40 Error...color register failure
50 Error...slot type conflict failure
51 memory conflict error
52 Error...ROM conflict error
60 DAC stuck low
61 DAC stuck low
62 DAC stuck low
63 Error...DAC stuck high
64 DAC fault
65 DAC fault
66 DAC fault
70 Error...bad alternate ROM version
80 Error...color gun stuck on
90 Error...color gun stuck off
A0 memory failure
F0 failure
00 Video POSY complete

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Text Messages


101 Option ROM Error
102 System board failure
103 System board failure
162 System options not set
163 Time and date not set
164 Memory size error
183 Invalid processor jumper setting
201 Memory error
202 Memory type mismatch
207 ECC corrected single bit errors in DIMM/SIMM pair(s)
213 Incompatible DIMM module in DIMM socket(s)
301 Keyboard error
304 Keyboard or system unit error
401 Parallel port 1 address assignment conflict
403 Parallel port 3 address assignment conflict
404 Parallel port address conflict detected
410 Audio interrupt conflict
411 Network interface card interrupt conflict
501 Display adapter failure
601 Diskette controller error
602 Diskette boot record error
605 Diskette drive type error
610 External storage device failure
611 Primary floppy port address assignment conflict
612 Secondary floppy port address assignment conflict
660 Display cache is detected unreliable
912 Computer cover has been removed since last system startup
914 Hood lock coil is not connected
916 thermal sensor from processor heatsink is not connected
917 Expansion riser not detected
1151 Serial port 1 address conflict detected
1152 Serial port 2 address conflict detected
1155 Serial port address detected
1201 System audio address conflict detected
1202 MIDI port address conflict detected
1203 Game port address conflict detected
1720 SMART hard drive detects imminent failure
1721 SMART SCSI hard drive detects imminent failure
1771 Primary disk port address assignment conflict
1772 Secondary disk port address assignment conflict
1780 Disk 0 failure
1781 Disk 1 failure
1782 Disk controller failure
1790 Disk 0 failure
1791 Disk 1 failure
1792 Secondary disk controller failure
1793 Secondary controller or disk failure
1800 Temperature alert
1801 Processor not supported by ROM BIOS




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