"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


See also Phoenix or (mostly) Award. AST introduced an enhanced BIOS in 1992 with 3 beeps before all early POST failure messages, for Field Replaceable Unit identification. Otherwise, the most significant (left) digit of the POST code indicates the number of long beeps, and the least significant (right) digit indicates the short beeps. 17 therefore means 1 long beep and 7 short. Doesn't work after 20. Errors below 20 are generally fatal.

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

00 Reserved; Beep and halt if error occurs
01 Test CPU registers
02 Test the 8042 keyboard controller buffer
03 Test the 8042 keyboard controller reset
04 Verify presence of keyboard and check communication
05 Read keyboard input port (WS386SX16)
06 Initialize system board support chipset
09 Test BIOS ROM checksum
0D Test 8254 programmable interrupt timer registers (13 short beeps)
0E Test ASIC registers (CLEM only, 14 short beeps)
0F Test CMOS RAM shutdown byte (15 short beeps)
10 Test DMA controller 0 registers
11 Test DMA controller 1 registers
12 Test DMA page registers (EGA.VGA vertical retrace failed)
13 EGA/VGA RAM test failed
14 Test memory refresh toggle (EGA/VGA CRT registers failed)
15 Test base 64KB memory
16 Set interrupt vectors in base memory
17 Initialize video
18 Test display memory
20 EISA bus board power on (EISA systems only)
30 Test programmable interrupt controller #1 mask register
31 Test programmable interrupt controller #2 mask register
32 Test programmable interrupt controller's for stuck interrupts
33 Test for stuck NMI (P386 25.33, P486, CLAM and EISA)
34 Test for stuck DDNIL status (CLEM only)
40 Test CMOS RAM backup battery
41 Calculate and verify CMOS checksum
42 Setup CMOS RAM options (except WS386SX16)
50 Test the protected mode
51 Test protected mode exceptions
60 Calculate RAM size
61 Test RAM
62 Test shadow RAM (WS386SX16, P386 25/33, P486, CLEM, EISA); test cache (P386/16)
63 Test cache memory (P386 25/33, P486, CLEM, EISA); copy video BIOS to shadow RAM (p386C, P386/16, WS386SX16)
64 Copy system BIOS to shadow RAM (P386 25/33, P486, CLEM,EISA); Copy video BIOS to shadow RAM (P386 16, WS386SX16)
65 Copy video BIOS to shadow RAM P386 25/33, P486, CLEM,EISA); Test cache (WS386SX16)
66 Test 8254 programmable interrupt timer channel 2 (P386 25/33, P486, EISA)
67 Initialize memory (Eagle only)


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