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The AMI BIOS Survival Guide v3.1go to Italian versiontranslate
The AMI BIOS Survival Guide v3.1
Edited by Jean-Paul Rodrigue
rodriguj@mistral.ere.umontreal.ca
Contributors
==================================
Gordon L. Burditt (gordon@sneaky.lonestar.org)
Peter Herweijer (pieterh@sci.kun.nl)
Kajetan Hinner (uf341ea@sunmail.lrz-muenchen.de)
Piotr Karocki (yskarock@cyf-kr.edu.pl)
Brian Lee (blee@bart.conestogac.on.ca)
Aad Offerman (offerman@einstein.et.tudelft.nl)
Keith Rohrer (rohrer@fncrd8.fnal.gov)
Jerome Schneider (jls@atg.com)
Cameron Spitzer (cls@truffula.sj.ca.us)
Andy Walton (akw@ukc.ac.uk)
Version history
==================================
Version 1.0 to 1.3: December 1993 (initial postings)
Version 2.0 to 2.4: January 1994 (the first "complete" versions)
Version 2.5 and 2.6 : February 1994 (vitamin C added)
Version 2.65 and 2.7: March 1994 (no cholesterol)
Version 3.0: 16-04-94 (new prune-strawberry-cabbage flavour)
Version 3.1: 13-05-94 (friday the 13th edition)
What's new in version 3.1 (*)
==================================
- FTP archive site available for the guide.
- A list of BIOS error messages (see section 2.4)
- Several additions to various topics (*).
Crossposted in:
==================================
comp.sys.ibm.pc.hardware, comp.sys.ibm.pc.hardware.chips,
comp.sys.ibm.pc.hardware.misc & comp.answers (patent pending).
(*) Archive Site
==================================
The guide, along with other hardware-related FAQs, is available through
anonymous FTP at rahul.net in the pub/cameron/PC-info directory. The
document is compressed by Gzip, available at any GNU archive sites like
gatekeeper.dec.com, in the pub/GNU directory.
What is the AMI BIOS survival guide?
==================================
BIOS settings are a frequent problem in several hardware related newsgroups.
Did you ever experienced a system lock up or poor performance and erratic
behaviour due to improper BIOS settings? Have you ever been let in the dark by
a cryptic 5 pages badly written motherboard manual? The answer is probably
yes. I took some initiative and decided to edit a FAQ for the AMI BIOS
(American Megatrends Inc.). This BIOS is, I believe, the most common. The
guide provides a description of each BIOS functions (at least those we are
aware of) and tips for their settings. I hope it will eventually help newbies
"decipher" BIOS settings and more advanced users "optimize" their system. It
could even keep you from a painful visit to your local computer store!
Disclaimer and other stuff
==================================
This document is provided "as is". The editor and contributors take no
responsabilities for any problems, damages, humiliations, world wars or loss
of sanity resulting from improper BIOS settings. If you are in doubt, please
post a question to the comp.sys.ibm.pc.hardware.chips newsgroup or refer to a
competent computer technician. Messing up with something you do not
understand will often get you in trouble (Who doesn't know someone who did?).
YOU HAVE BEEN WARNED.
This guide is provided as a free reference for the usenet (internet)
community. You may distribute it freely as long as the contents are not
altered, no fees are asked, and references to the editor and contributors are
kept. If you are making money out of this file or posting net-wide (to groups
where it does not belong) religious babblings or green card lottery scam: may
your CPU perish by electromigration!
I want to know more...
==================================
If you have an UNSOLVED BIOS problem not described herein, please post it to
related newsgroups (like comp.sys.ibm.pc.hardware.chips), NOT to the editor or
the contributors. You should also have a look at the ibm.pc.hardware.*
Frequently Asked Questions (FTP rtfm.mit.edu; directory:
/pub/usenet/news.answers/csiph-faq; filenames: part1 to part5) posted
regularly. It contains a wealth of information about computer hardware. Look
also in the comp.answers newsgroup for available FAQs.
If you have a SOLVED problem, please send it to the editor so it can be added
to subsequent versions of this document. Your contributions or comments will
be much appreciated. If you want the most recent version of this document,
please e-mail the editor and tell what version you currently have. If a more
recent version is available, it will be fowarded. Before doing so, please look
in this newsgroup for a regular posting of this guide.
If you want various technical information about AMI BIOS, you can find it at
the FTP site AMERICAN.MEGATRENDS.COM. If you can afford long distance
charges, try the AMI BBS at (404) 246-8780 (or 8781, 8782, 8783). There is
also a shareware named AMISETUP that enables BIOS settings and provides an
on-line reference (for registered versions). It can even let you access some
settings that could not be accessed otherwise. You can find it at SIMTEL
mirror sites like FTP.WUSTL.EDU or OAK.OAKLAND.EDU in the
/systems/ibmpc/msdos/sysutil directory. The file name is AMISE260.ZIP.
One last thing...
==================================
I would like to thank the contributors to have taken some of their time to
write varied topics and provide enlightening feedbacks. Some parts of this
document are still incomplete and some information may be inaccurate. Your
feedbacks will help this document be as accurate and up to date as possible. I
am sorry if I cannot answer to everyone or add everything that is send to me.
I would also like to thank the following persons for providing information on
specific topics: Michiel de Vries, Andy Eskilsson, Doug Hogarth, Reinhard
Kirchner, Mirek Komon, Jim Kozma, Juha Laiho, Alain Lavoie, Erik Mouw, Chris
Pollard, Dietrich Schmidt, Hans Schrader, Loren Schwiebert, Dan Sobel, Dave
Spensley and Dmitry Stefankov.
TABLE OF CONTENT
==================================
1.0 DEFINITIONS
1.1 BIOS
1.2 CMOS
1.3 Chipset
2.0 POST AND ENTERING SETUP
2.1 A Typical AMI BIOS POST Sequence
2.2 AMI BIOS POST Errors
2.3 Other AMI BIOS POST Codes
(*) 2.4 BIOS Error Messages
3.0 STANDARD CMOS SETUP
4.0 ADVANCED CMOS SETUP
5.0 ADVANCED CHIPSET SETUP
6.0 AUTO CONFIGURATION WITH BIOS DEFAULTS
7.0 AUTO CONFIGURATION WITH POWER-ON DEFAULTS
8.0 CHANGE PASSWORD
9.0 HARD DISK UTILITY
9.1 Hard Disk Format
9.2 Auto Detect Hard Disk
9.3 Auto Interleave
9.4 Media Analysis.
10.0 WRITE TO CMOS AND EXIT
11.0 DO NOT WRITE TO CMOS AND EXIT
12.0 FREQUENTLY ASKED QUESTIONS (FAQ)
1.0 DEFINITIONS
==================================
1.1 BIOS: Basic Input Output System. Computer hardware has to work with
software, so it needs an interface with it. The BIOS gives the computer a
little built-in starter kit to run the rest of softwares from floppy disks
(FDD) and hard disks (HDD). The BIOS is responsible for booting the computer
by providing a basic set of instructions. It performs all the tasks that need
to be done at start-up time: POST (Power-On Self Test, booting an operating
system from FDD or HDD). Furthermore, it provides an interface to the
underlying hardware for the operating system in the form of a library of
interrupt handlers. For instance, each time a key is pressed, the CPU
(Central Processing Unit) perform an interrupt to read that key. This is
similar for other input/output devices (Serial and parallel ports, video
cards, sound cards, hard disk controllers, etc...). Some older PC's cannot
co-operate with all the modern hardware because their BIOS doesn't support
that hardware. The operating system cannot call a BIOS routine to use it;
this problem can be solved by replacing your BIOS with an newer one, that does
support your new hardware, or by installing a device driver for the hardware.
1.2 CMOS: Complementary Metal Oxide Semiconductor. To perform its tasks, the
BIOS need to know various parameters (hardware configuration). These are
permanently saved in a little piece (64 bytes) of CMOS RAM (short: CMOS). The
CMOS power is supplied by a little battery, so its contents will not be lost
after the PC is turned off. Therefore, there is a battery and a small RAM
memory on board, which never (should...) loses its information. The memory
was in earlier times a part of the clock chip, now it's part of such a highly
Integrated Circuit (IC). CMOS is the name of a technology which needs very
low power, so the computer's battery is not too much in use. Actually there
is not a battery on new boards, but an accumulator (Ni_Cad in most cases). It
is recharged every time the computer is turned on. If your CMOS is powered by
external batteries, be sure that they are in good operating condition. Also,
be sure that they do not leak. It may damage the motherboard. Otherwise,
your CMOS may suddenly "forget" its configuration and you may be looking for a
problem elsewhere. In the monolithic PC and PC/XT this information is
supplied by setting the DIP (Dual-In-line Package) switches at the motherboard
or peripheral cards. Some new motherboards have a technology named the Dallas
Nov-Ram. It eliminates having an on-board battery: There is a 10 year lithium
cell epoxyed into the chip.
1.3 Chipset: A PC consists of different functional parts on its motherboard:
ISA (Industry Standard Architecture), EISA (Enhanced Industry Standard
Architecture) VESA (Video Enhanced Standards Association) and PCI (Peripheral
Component Interface) slots, memory, cache memory, keyboard plug etc... The
chipset enables a set of instructions so the CPU can work (communicate) with
other parts of the motherboard. Nowadays most of the discrete chips; PIC
(Programmable Interrupt Controller), DMA (Direct Memory Access), MMU (Memory
Management Unit), cache, etc... are packed together on one, two or three
chips; the chipset. SETUP allows you to change the parameters with which the
BIOS configures your chipset. Since chipsets of a different brand are not the
same, for every chipset there is a BIOS version. Now we have fewer and fewer
chipsets which do the job. Some chipsets have more features, some less. OPTi
is such a commonly used chipset. In some well integrated motherboards, the
only components present are the CPU, the two BIOS chips (BIOS and Keyboard
BIOS), one chipset IC, cache memory (DRAMs, Dynamic Random Access Memory),
memory (SIMMs, Single Inline Memory Module, most of the time) and a clock
chip.
2.0 POST AND ENTERING SETUP
==================================
When the system is powered on, the BIOS will perform diagnostics and
initialize system components, including the video system. (This is
self-evident when the screen first flicks before the Video Card header is
displayed). This is commonly refered as POST (Power-On Self Test). Afterwards,
the computer will proceed its final boot-up stage by calling the operating
system. Just before that, the user may interupt to have access to SETUP.
To allow the user to alter the CMOS settings, the BIOS provides a little
program, SETUP. Mostly setup can be entered by pressing a special key
combination (DEL, ESC, CTRL-ESC, or CRTL-ALT-ESC) at boot time (Some BIOSes
allow you to enter setup at any time by pressing CTRL-ALT-ESC). The AMI BIOS
is mostly entered by pressing the DEL key after resetting (CTRL-ALT-DEL) or
powering up the computer. You can bypass the extended CMOS settings by
holding the key down during boot-up. This is really helpful, especially
if you bend the CMOS settings right out of shape and the computer won't boot
properly anymore. This is also a handy tip for people who play with the older
AMI BIOSes with the XCMOS setup. It allows changes directly to the chip
registers with very little technical explanation.
2.1 A Typical AMI BIOS POST Sequence
------------------------------
a) Display some basic informations about the video card like its brand, video
BIOS version and video memory available.
b) Display the BIOS version and copyright notice in upper middle screen. You
will see a large sequence of numbers at the bottom of the screen. They refer
to the BIOS serial number, version and type of chipset. (*) For versions
1986-1991 (AMIBIOS before HI-Flesh):
Reference number: ABBB-NNNN-MMDDYY-KX, where
A = D for BIOS with Diagnostics.
= S for BIOS with Setup program.
= E for BIOS with Extended Setup program.
BBB = C&T for C&T386 chipset.
= NET for C&T NEAT chipset.
= 286 fpr standard 286,VLSI,G2 286 boards.
= SUN for SUNTAC 286 boards.
= PAQ for COMPAQ compatible 386 boards.
= INT for INTEL boards.
= AMI for AMI 386 motherboard.
= G23 for G2 386 board.
= ??? other n/a.
NNNN = reference number for manufacturer.
MMDDYY = BIOS release date.
KX = AMI keyboard BIOS version number (X = usually
1,2,3,etc).
(could someone provide information for recent BIOS serial numbers?)
c) Display memory count. You will also ear tick sounds if you have enabled it
(see Memory Test Tick Sound section).
d) Once the POST have succeeded and the BIOS is ready to call the operating
system (DOS, OS/2, NT etc...) you will see a basic table of the system's
configurations:
Main Processor: The type of CPU identified by the BIOS. Usually
Cx386DX, Cx486DX, etc..
Numeric Processor: Present if you have a FPU or None on the contrary. If
you have a FPU and the BIOS does not recognize it,
see section Numeric Processor Test in Advanced CMOS
Setup.
Floppy Drive A: The drive A type. See section Floppy drive A in
Standard CMOS Setup to alter this setting.
Floppy Drive B: Idem.
Display Type: See section Primary display in Standard CMOS Setup.
AMIBIOS Date: The revision date of your AMI BIOS. Useful to mention
when you have compatibility problems with adaptor
cards (notably fancy ones).
Base Memory Size: The number of KB of base memory. Usually 640.
Ext. Memory Size: The number of KB of extended memory.
NOTE: In the majority of cases, the summation of base memory and extended
memory does not equal the total system memory. For instance in a 4096 KB
(4MB) system, you will have 640KB of base memory and 3072KB of extended
memory, a total of 3712KB. The missing 384KB is reserved by the BIOS, mainly
as shadow memory (see Advanced CMOS Setup).
Hard Disk C: Type: The master HDD number. See Hard disk C: type section
in Standard CMOS Setup.
Hard Disk D: Type: The slave HDD number. See Hard disk D: type section
in Standard CMOS Setup.
Serial Port(s): The hex numbers of your COM ports. 3F8 and 2F8 for
COM1 and COM2.
Parallel Port(s): The hex number of your LTP ports. 378 for LPT1.
Right under the table, BIOS usually display the size of cache memory. Common
sizes are 64KB, 128KB or 256KB. See External Cache Memory section in Advanced
CMOS Setup.
2.2 AMI BIOS POST Errors
------------------------------
During the POST routines, which are performed each time the system is powered
on, errors may occur. Non-fatal errors are those which, in most cases, allow
the system to continue the boot up process. The error messages normally
appear on the screen. Fatal errors are those which will not allow the system
to continue the boot-up procedure. If a fatal error occurs, you should
consult with your system manufacturer or dealer for possible repairs. These
errors are usually communicated through a series of audible beeps. The
numbers on the fatal error list correspond to the number of beeps for the
corresponding error. All errors listed, with the exception of #8, are fatal
errors. All errors found by the BIOS will be put into I/O port 80h.
1 DRAM refresh failure. The memory refresh circuitry on
the motherboard is faulty.
2 Parity Circuit failure. A parity error was detected in the
base memory (first 64k Block) of the system.
3 Base 64K RAM failure. A memory failure occured
within the first 64k of memory.
4 System Timer failure. Timer #1 on the system board has
failed to function properly.
5 Processor failure. The CPU on the system board has
generated an error.
6 Keyboard Controller 8042-Gate A20 error. The
keyboard controller (8042) contains the gate A20 switch
which allows the computer to operate in virtual mode.
This error message means that the BIOS is not able to
switch the CPU into protected mode.
7 Virtual Mode (processor) Exception error. The CPU on
the motherboard has generated an Interrupt Failure
exception interrupt.
8 Display Memory R/W Test failure. The system video
adapter is either missing or Read/Write Error its memory
is faulty. This in not a fatal error.
9 ROM-BIOS Checksum failure. The ROM checksum
value does not match the value encoded in the BIOS.
This is good indication that the BIOS ROMs went bad.
10 CMOS Shutdown Register. The shutdown register for the
CMOS memory Read/Write Error has failed.
(*)11 Cache Error / External Cache Bad. The external cache
is faulty.
2.3 Other AMI BIOS POST Codes
------------------------------
2 short beeps: POST failed. This is caused by a failure of one of the
hardware testing procedures.
1 long & 2 short
beeps: Video failure. This is caused by one of two possible
hardware faults. 1) Video BIOS ROM failure,
checksum error encountered. 2) The video adapter
installed has a horizontal retrace failure.
1 long & 3 short
beeps: Video failure. This is caused by one of three possible
hardware problems. 1) The video DAC has failed. 2)
the monitor detection process has failed. 3) The video
RAM has failed.
1 long beep: POST passed. This indicates that all hardware tests
were completed without encountering errors.
If you have access to a POST Card reader, (Jameco, etc) you can watch the
system perform each test by the value that's displayed. If/when the system
hangs (if there's a problem) the last value displayed will give you a good
idea where and what went wrong, or what's bad on the system board. Of course,
having a description of those codes would be helpful, and different BIOSes
have different meanings for the codes. (could someone point out FTP sites
where we could have access to a complete list of error codes for different
versions of AMI BIOS?).
(*)2.4 BIOS Error Messages
------------------------------
This is a short list of most frequent on-screen BIOS error messages. Your
system may show them in a different manner. When you see any of these,
you are in trouble - Doh! (Does someone has any additions of
corrections?)
"8042 Gate - A20 Error" : Gate A20 on the keyboard controller
(8042) is not working.
"Address Line Short!" : Error in the address decoding circuitry.
"Cache Memory Bad,
Do Not Enable Cache!" : Cache memory is defective.
"CH-2 Timer Error" : There is an error in timer 2. Several
systems have two timers.
"CMOS Battery State Low" : The battery power is getting low. It
would be a good idea to replace the battery.
"CMOS Checksum Failure" : After CMOS RAM values are saved, a
checksum value is generated for error
checking. The previous value is different
from the current value.
"CMOS System Options
Not Set" : The values stored in CMOS RAM are
either corrupt or nonexistent.
"CMOS Display Type
Mismatch" : The video type in CMOS RAM is not the
one detected by the BIOS.
"CMOS Memory Size
Mismatch" : The physical amount of memory on the
motherboard is different than the amount in
CMOS RAM.
"CMOS Time and Date
Not Set" : Self evident.
"Diskette Boot Failure" : The boot disk in floppy drive A: is corrupt
(virus?). Is an operating system present?
"Display Switch Not
Proper" : A video switch on the motherboard must
be set to either color or monochrome.
"DMA Error" : Error in the DMA controller.
"DMA #1 Error" : Error in the first DMA channel.
"DMA #2 Error" : Error in the second DMA channel.
"FDD Controller Failure" : The BIOS cannot communicate with the
floppy disk drive controller.
"HDD Controller Failure" : The BIOS cannot communicate with the
hard disk drive controller.
"INTR #1 Error" : Interrupt channel 1 failed POST.
"INTR #2 Error" : Interrupt channel 2 failed POST.
"Keyboard Error" : There is a timing problem with the
keyboard.
"KB/Interface Error" : There is an error in the keyboard
connector.
"Parity Error ????" : Parity error in system memory at an
unknown address.
"Memory Parity Error
at xxxxx": : Memory failed at the xxxxx address.
"I/O Card Parity Error
at xxxxx": An expansion card failed at the xxxxx
address.
"DMA Bus Time-out" : A device has used the bus signal for more
than allocated time (around 8
microseconds).
NOTE: If you encounter any POST error, there is a good chance that it is an
HARDWARE related problem. You should at least verify if adaptor cards or
other removable components (simms, drams etc...) are properly inserted before
calling for help.
3.0 STANDARD CMOS SETUP
==================================
WARNING: You should have your current setup options written down ON PAPER
somewhere, preferably taped to the inside or the outside of the case. CMOS
memory has a tendency to get erased as the battery gets old, or become
inaccessible if you forget the password. Especially remember the hard disk
settings; they are the most important.
NOTE: There are several good CMOS saver programs out on the market, including
the PC-Tools and Norton recovery programs. They allow a user to save a copy
of the CMOS registers to a file in case the battery dies, or they mess around
with the settings, etc...
Date (mn/date/year) : To change the date of the system clock.
Time (hour/min/sec) : To change the time of the system clock.
Hard disk C: Type : The number of your primary (master) hard drive. Most of
the time this number is 47, which means that you must specify
the drive specs according to your hard drive manual:
Cyln : The number of cylinders on your hard disk.
Head : The number of heads.
WPcom : Write Precompensation. Older HDD's have the same
number of sectors per track at the innermost tracks as at the
outhermost tracks. This means that the data density at the
innermost tracks is higher and thus the bits are lying closer
together. Normally the data is written like this:
+ + - + - + + + - - - +
Areas having the same direction tend to float away from
eachother and areas having opposite direction tend to float
towards eachother:
+ + - + - + + + - - - +
making the data less reliable after some time. To avoid this,
starting from the WP cylinder, bits are written on the surface
like this:
+ + - + - + + + - - - +
making your data last longer. Starting with this Cyl# until
the end of Cyl#s the writing starts earlier on the disk. In
modern HDs (all AT-BUS and SCSI, Small Computer Systems
Interface) this entry is useless. Set it either to -1 or max
Cyln. For IDE (Integrated Device Electronics) HDD's it is not
necessary to enter a WP cylinder. The IDE HDD will ignore it
for it has its own parameters aboard.
LZone : The address of the landing zone. Same as WPcom. Used
in old HDs without an auto-parking feature (MFM, Modified
Frequency Modulated, or RLL, Run Length Limited). Set it to 0
or max Cyl#.
Sect : The number of sectors per track.
Size : This is automatically calculated according the number
of cylinders, heads and sectors. It is in megabytes.
NOTE: There is a shareware program called ANYDRIVE that will allow you to set
up hard drive geometries not supported in your BIOS. This should be available
on your favourite local BBS (Any internet FTP site for this one?). Note that
it only sets the correct geometry, many older BIOSes have timing problems with
IDE drives and this type of problem will not be helped by ANYDRIVE. (*) You
can also use the freeware program HD-MBOOT from the archive file DSUTIL12.ZIP
on the Internet: SIMTEL20 or its mirrors, and GARBO FTP-sites in the directory
/MSDOS/TURBOPAS or PC/TURBOPAS.
Hard disk D: Type : The number of your secondary (slave) hard drive. Same
procedure than above. Jumpers must be set for an hard drive to
perform as slave. Please refer to your hard drive manual. You
might also want to refer to the hard disk data file frequently
posted to comp.sys.ibm.pc.hardware.
Floppy drive A : The type of floppy drive installed for drive A. Frequent
configurations are 1.44 MB (3 1/2 inches), or 1.2 MB (5 1/4).
Newer systems have also a 2.88 MB (3 1/2) setting.
Floppy drive B : The type of floppy drive installed for drive B.
Primary display : The type of displaying standard you are using. The most
frequent is VGA/PGA/EGA. Modern computers have VGA (Video
Graphics Array). If you have an older black/white display
select Mono or Hercules, if your Video adapter card is text
only, select MDA.
Keyboard : Installed. If 'not installed' this option sets the BIOS to
pass the keyboard test in the POST, allowing to reset a PC
without a keyboard (file server, printer server, etc.), without
the BIOS producing a keyboard error.
4.0 ADVANCED CMOS SETUP
==================================
WARNING: May vary according to your system and your BIOS version. Some
functions may not be present or the order and name may be different.
ADDITIONAL WARNING: Know *exactly* what you are doing. Some configurations
may keep your computer off from booting. If that's the case: Switch the power
off. Turn your computer on *while* keeping the DEL key pressed. Some
mainboards will come up again. If it still doesn't boot, consult your
motherboard manual. Look for a "forget CMOS RAM" jumper. Set it. Try it
again. If it still doesn't boot, ask a friend or post to this newsgroup. You
are permitted to panic. See note in section 3.0.
Typematic Rate
Programming : Disabled. It enables the typematic rate
programming of the keyboard. Not all keyboards
support this! The following two entries specify how
the keyboard is programmed if enabled.
Typematic Rate Delay
(msec) : 500. The initial delay before key auto-repeat
starts. I.e. how long you've got to press a key
before it starts repeating.
Typematic Rate (Chars/Sec) : 15. It is the frequency of the auto-repeat
i.e. how fast a key repeats.
Above 1 MB Memory Test : If you want the system to check the memory above 1
MB for errors. Disabled recommended for faster boot
sequence. The HIMEM.SYS driver for DOS 6.2 now
verifies the XMS (Extended Memory Specification), so
this test is redundant. Alternatively, you can enable
this test and disable HIMEM.SYS from doing so. (*) It
is preferrable to use the XMS test provided by
HIMEM.SYS since it is operating in the real
environment (where user wait states and other are
operational).
Memory Test Tick Sound : Enabled recommended. It gives an audio record that
the boot sequence is working properly. Plus, its
aural confirmation of your CPU clock speed/Turbo
switch setting (for trained users!).
Memory Parity Error
Check : Enabled recommended. Additional feature to test bit errors
in the memory. All (or almost all) PC's check their memory
during operation. Every byte in memory has another ninth bit,
that with every write access is set in such way that the parity
of all bytes is odd. With every read access the parity of a
byte is checked for this odd parity. If a parity error occurs,
the NMI (Non Maskable Interrupt), an interrupt you mostly
cannot switch off, so the computer stops his work and displays
a RAM failure) becomes active and forces the CPU to enter an
interrupt handler, mostly writing something likes this on the
screen: PARITY ERROR AT 0AB5:00BE SYSTEM HALTED. On some
motherboards you can disable parity checking with standard
memory. Enabled to be sure data from memory are correct.
Disable only if you have 8-bit RAM, which some vendors use
because it's 10% cheaper. If you own a Gravis Ultrasound
Soundcard (GUS), it's imperative that this is enabled;
otherwise the Sound Blaster emulation won't work(!).
Hard Disk Type 47
RAM Area : The BIOS has to place the HD type 47 data somewhere in memory.
You can choose between DOS memory or PC BIOS (or peripheral card)
memory area 0:300. DOS memory is valuable, you only have 640KB of
it. So you should try to use 0:300 memory area instead. There may
be some peripheral card which needs this area too (soundcard,
network, whatever). So if there are some fancy cards in your PC,
check the manuals if they're using the 0:300 area. But in most
cases this will work without checking. (*) This is redundant if BIOS
is shadowed (may be not in very old BIOSes). The RAM area can be
verified by checking address of int41h and int46h. These are fixed
disk parameters blocks. If they point to the BIOS area, BIOS made
modification of parameters before mapping RAM there.
Wait for
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