"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

Landmark POST Codes

Comes with POST card and replaces that in motherboard being tested; same as BIOSYS BIOS. Beeps as for IBM AT. Codes sent to ports 280 and 80.

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

Jumpstart XT


01 Jump to reset area in BIOS ROM
02 Initialize DMA page register
03 Initialize DMA refresh register
04 Clear all RAM
05 Perform RAM test on first 64KB
06 Clear first 64KB
07 Initialize BIOS stack to 0FC0h
08 Set the equipment flag based on XT switches
09 Initialize default-interrupt vectors
0A Initialize the 8255 parallel interface, if it exists
0B Initialize the 8259 PIT and enable interrupts
0C Setup adapters and peripherals
0D Setup video system
0E Initialize the video system
0F Initialize the equipment
10 Initialize memory configuration
11 Setup system timer function
12 Initialize system timer
13 Setup time-of-day function
14 Initialize time of day from RTC data
15 Setup and initialize "print screen" function
16 Setup and initialize cassette interface, if available
17 Setup and initialize bootstrap function
18 Setup and initialize keyboard function
19 Enable speaker
1A Setup system timer
1B Enable the RTC
1C Setup timer 2
1D Determine memory size; write 55Aa/AA55 to first and last word in segment
1E Read first and last word of segment
1F Compare first and last words
20 Report found memory size of segment
21 Perform BIOS ROM checksum test
22 Perform complete RAM testing on cold boot
23 Move system stack to bottom of memory and save pointer 40:0E
24 Reset parity after RAM sizing
25 Enable timer and keyboard interrupts
26 Setup the serial and parallel ports
27 Setup the game port
28 Setup the floppy-disk controller
29 Scan for optional ROM's in 2KB chucks from C8000h
2A Call the boot loader

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Jumpstart AT


03 Sound one short beep
04 Initialize the bell tone
05 Enable CMOS RAM
06 Reset video controller
07 Disable parity checking
08 Start memory refresh
09 Clear the reset flag in RAM
0A Test DMA page registers
10 Use CMOS to determine if a soft reset has occurred
11 Check BIOS ROM checksum
12 Test system timer A
13 Test DMA channel 0
14 Test DMA channel 1
15 Test memory refresh
16 Flush 8042 keyboard controller input buffer
17 Reset 8042 keyboard controller
18 Get keyboard type
19 Initialize the keyboard
1A Clear any existing parity
1B Enable on-board parity
1C Test base 64KB memory
1D Test base 64K parity
1E Initialize POST stack
20 Check keyboard type
21 Test protected mode CPU registers
22 Initialize 8259 programmable interrupt controller
23 Initialize all interrupts
24 Test all interrupts
25 Perform DRAM checksum
26 Adjust configuration based on hardware found and CMOS settings
27 Check for presence of manufacturing switch
28 Initialize video controller
2A Test video memory
2B Test video sync
2C Check for auxiliary video controller
2D Change video configuration
2F Initialize the video system
30 Change video interrupt
31 Display any POST messages
32 Test memory and calculate size
33 Adjust memory configuration
34 Enable I/O parity
35 Test 8259 programmable interrupt controller
36 perform byte-swap test
37 Test NMI
38 Perform timer test
39 Initialize system timer A
3A Protected mode memory test
3B Test keyboard
3C Test keyboard interrupt
3D Enable A20
3E Reset hard disk controller
3F Setup floppy disk controller
40 Test floppy drive system
41 Setup keyboard
42 Enable interrupt timer
43 Check for dual floppy disk/hard disk controller
44 Locate floppy drive A
45 Locate floppy drive B
46 reset hard disk controller
47 Enable slave DMA
48 Locate any external ROM's
49 Initialize the parallel ports
4A Initialize the serial ports
4B Initialize the math coprocessor
4C Read CMOS RAM status
4D Check CMOS configuration against detected hardware
4E Initialize timer ticks
4F Enable IRQ9
50 Enable on-board parity
51 Run any add-on ROM's
52 Enable keyboard interrupt
53 Reset the parallel port
60 Check for any errors
61 Sound one short beep
62 Print sign-on message
64 Call interrupt 19 boot loader

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Supersoft AT


11 CPU register or logic error
12 ROMPOST A checksum error
13 ROMPOST B checksum error
14 8253 programmable interrupt timer channel 0
15 8253 programmable interrupt timer channel 1
16 8253 programmable interrupt timer channel 2
17 8237 DMA controller 1 error
18 8237 DMA controller 2 error
19 DMA page register error
1A 8042 keyboard controller error
21 Scan 16KB critical RAM error
22 Memory refresh error
23 CPU protected mode error
24 8259 interrupt controller 1 error
25 8259 interrupt controller 2 error
26 Unexpected interrupt detect
27 Interrupt 0, system timer, error
28 CMOS RTC error
29 NMI error
2A Locate and test math coprocessor
31 Keyboard controller error
32 Stuck key detected or CMOS RAM error
33 Floppy controller error
34 Floppy disk read error
35 MDA video memory error
36 Color video memory error
37 EGA/VGA RAM error
38 BIOS ROM checksum error
41 Memory error
42 Refresh fault
43 Display problem
44 Display problem
45 Display problem
59 No monitor detected

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