"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."

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

 Chips & Technologies
 Faraday A-Tease

Arche POST Codes

These come from the AMI BIOS (9 April 90) and use port 80h. Certain codes appear if a copy is made without AMI's copyright notice included. The major differences are at the end.

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

01 Disable the NMI and test CPU registers
02 Verify the BIOS ROM checksum (32KB at F8000h)
03 Initialize the keyboard controller and CMOS RAM communication
04 Disable the DMA and PIT; test the CMOS RAM interrupt
05 Reset the video controller
06 Test the 8254 programmable interrupt timer
07 Test delta count timer channel 2 (speaker)
08 Test delta count timer channel 1 (memory refresh)
09 Test delta count timer channel 0 (system timer)
0A Test parity circuit and turn on refresh
0B Enable parity check and test system timer
0C Test refresh trace link toggle
0D Test refresh timing synchronization
10 Disable cache and shadow memory; test the 64KB base memory
11 Perform 64KB memory read/write test
12 Initialize interrupt vector table in lower 1KB of RAM
14 Test CMOS RAM shutdown register...disable DMA and interrupt controllers
15 Test CMOS RAM battery and checksum
16 Test for floppy drive, based on CMOS setup...initialize monochrome video
17 Initialize CGA video
18 Clear the parity status (if any)
19 Test for EGA/VGA video BIOS at C0000h and pass control
1A Return from video ROM
1B Test primary video adapter...test video memory
1C Test secondary video adapter...test video memory
1D Compare CMOS settings to video adapter
1E Set video mode according to CMOS settings
20 Display CMOS RAM read/write errors and halt
21 Set cursor and call interrupt 10 to display status message
22 Display power on message; "386 BIOS"; check if CPU speed is 25Mhz or 33Mhz
23 Read new cursor position
24 Display AMI copyright message at the bottom of the screen
25 Test shadow RAM
F0 Shadow RAM test failed
30 Ready to enter protected mode
31 Enter protected mode (A20 gate) and enable timer interrupt (IRQ 0)
32 Get memory size above 1MB
33 Get memory size below 640KB
34 Test memory above 1MB
35 Test memory below 1MB
37 Clear memory below 1MB
38 Clear memory above 1MB
39 Use CMOS shutdown byte and return to real mode
3A Test 64KB read/write
3B Test RAM below 1MB and show the area being tested
3C Test RAM above 1MB and show the area being tested
3D RAM test complete OK
3E Ready to return to real mode
3F Back in real mode
40 Disable A20 gate
41 Check for AMI copyright message in ROM
42 Display the AMI copyright message, if found
43 Test cache memory; Clear <Esc> message
4E Process shutdown 1; Return to real mode
4F Restore interrupt vectors and data in BIOS RAM area
50 Test DMA controller
51 Initialize DMA controller
52 Test the DMA controller with patterns
54 Test DMA controller latches
55 Initialize and enable DMA controllers 1 and 2
56 Initialize 8259 programmable interrupt controllers
57 Test 8259 programmable interrupt controllers and setup interrupt mask registers
61 Check DDNIL status bit and display message
70 Perform keyboard (BAT) basic assurance test
71 Program keyboard to AT type
72 Disable keyboard and initialize keyboard circular buffer
73 Display message and initialize floppy controller and drive
74 Attempt to access the floppy drive
75 If the CMOS RAM is good, check and initialize the hard disk controller and drive
76 Attempt to access the hard disk drive
77 Shuffle and internal error codes
79 Check CMOS RAM battery and checksum...clear parity status
7A Compare size of base/extended memory to CMOS information
7B Unknown AMI function
7C Display AMI copyright
7D Set AT memory expansion bit
7E Verify the ROM contains and AMI copyright
7F Clear the <Del> message from the display...check if <Del> was pressed
80 Locate option ROM at C800h to DE00h and pass control to any found
81 Return from option ROM and initialize timer and data area
82 Setup parallel and serial ports
83 Test for math coprocessor
84 Check if keyboard is locked
85 Display any soft error messages
86 Test for option ROM at E0000h
A0 Error found in 256KB or 1MB RAM IC in lower 640KB
A1 Base 64KB random access and data pattern test (only in 386APR and Presto 386SX BIOS)
A9 Initialize on board VGA controller (Presto 386SX BIOS)
B0 Error in 256KB RAM IC in 640KB
B1 Base 64KB random access and data pattern test (only in Presto 386SX BIOS)
E0 Return to real mode and initialize base 64KB RAM (Presto)
E1 Initialize 640KB RAM (Presto)
EF Configuration memory error - can't find memory
F0 Test shadow RAM from 04000h
00 Call the interrupt 19 boot loader


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