CMOS.TXT

Purpose
*******

1. Naive users sometimes meddle with CMOS settings. We need a
fast way to put the scores of subtle CMOS configuration settings
back the way they were.

2. Power surges can corrupt CMOS. We need a way for a naive
user to quickly restore all the CMOS settings.

3. If the battery fails, the contents will be lost. We need a
way to restore a known working CMOS configuration.


Syntax
******

There are three utilities in the CMOS suite:

CMOSSAVE.COM A:Myfile.Sav
IF ERRORLEVEL 1 GO TO Trouble

- saves a copy of CMOS in a file on hard disk or floppy.

CMOSREST.COM A:MyFile.Sav
IF ERRORLEVEL 1 GO TO Trouble

- restores CMOS from a file on hard disk or floppy.

CMOSCHK.COM A:MyFile.Sav
IF ERRORLEVEL 1 GO TO FixIt

- checks that CMOS has not been meddled with since the
last CMOSSAVE. Compares CMOS with a file on hard disk
or floppy.

Hints on Use
************

Do a CMOSSAVE both to hard disk and to floppy. The hard disk
copy can be used for quick restores built into your AUTOEXEC.BAT
file.

CMOSCHK.COM C:\MyCMOS.Sav
IF ERRORLEVEL 1 CMOSREST.COM C:\MyCMOS.Sav

At that point you must reboot before the restored cmos settings
take effect. See CHKSAVE.BAT for a realistic way to handle
this.

Sometimes CMOS will be so badly damaged the hard disk parameters
will be corrupt and your hard disk will stop working. In that
case you will have to revert to using the floppy copy.

Whenever you change your CMOS setting deliberately, you need to
redo the CMOSSAV.COM. However USE A NEW FILENAME, so that you
can easily revert to the old version if your new settings do not
pan out.

How it works
************

CMOSSAVE.COM simply copies the 128 byte contents of the CMOS
bytes to a file. CMOSREST.COM copies them back. CMOSCHK
compares them with the file contents. If they are not equal it
sets ERRORLEVEL 1.

CMOSREST does not touch bytes 0 to 09 and 32h because these are
volatile -- they contain the date and time. Similarly CMOSCHK,
does not panic if any of these volatile bytes differ. However,
CMOSSAVE saves all 128 bytes, so that you can browse the
generated file with a hex editor to learn more about how CMOS
works.

Because CMOSSave also saves the extended CMOS bytes, CMOSRest
will restore the esoteric options like shadow RAM, wait states,
processor clock speed, HMA enable etc.

These is no need to calculate checksums, since the checksum is
saved and restored just like any other CMOS byte.

I have included a file called CHKCMOS.BAT which can be inserted
in your AUTOEXEC.BAT which uses all three utilities.


How CMOS is used
****************

CMOS is battery backed RAM that stores configuration information
when the power is off. It is on my top ten worst ideas list of
all time. The problem is, CMOS is far too easily corrupted, by
programs, power or meddling.

offset purpose
00 seconds time of day
01 seconds alarm
02 minutes time of day
03 minutes alarm
04 hours time of day
05 hours alarm
06 day of week
07 alarm day of month
08 month of year
09 year 1980=0
0A status register A
!0B status register B alarm
0C status register C flags
!0D status register D battery
!0E diagnostics status
!0F shutdown status
!10* diskette type
!11* reserved
!12* hard disk type
!13* reserved
!14* LSB equipment word
!15* LSB base RAM in K
!16* MSB base RAM in K
!17* LSB expansion RAM in K
!18* MSB expansion RAM in K
!19* fixed disk type C: extension
!1A* fixed disk type D: extension
!1B*.2D reserved
!2E* MSB checksum
!2F* LSB checksum
!30 LSB extended RAM in K above 1 MB
!31 MSB extended RAM in K above 1 MB
32 BCD Century
!33 128K info status byte
!34..3F reserved
!40..79 reserved for use by chipset maker

! = must be restored
* = checksummed

Troubleshooting
***************

Sometimes your CMOS will be so wrecked you cannot even get your
machine limping enough to run CMOSREST from floppy. In that
case you must clear CMOS. Do this on AMI BIOSes by holding down
the INS key, powering off, powering on, then releasing the INS
key. In the worst case, remove the battery and let the
capacitance on the board drain overnight to clear it.

You can then get a bare bones CMOS configured -- that just has
the floppies right. From there you can run CMOSREST.COM.

What is considered volatile and what is not, might vary for
different boards. If you have trouble restoring, DO NOT
DESPAIR. All is recorded. A variant of the CMOSREST program
could get you back. All you need is the source.


Author
******

CMOSSAVE, CMOSREST and CMOSCHK are copyrighted but may be freely
used for any purpose except military. MASM source is available.
If you pass the files on, PLEASE PASS ON THIS DOCUMENTATION TOO.

Please report bugs and problems to:
Roedy Green
Canadian Mind Products
#168 - 1020 Mainland Street
Vancouver BC Canada
V6B 2T4
(604) 684-6529

Electronic mail users can contact me on:
BIX id ROEDY
Zoomit id GREEN ROEDY

Harvey Fishman wrote a pair of programs similar to CMOSSAVE and
CMOSREST, but to the best of my knowledge, never released them.

Shareware Status
****************

CMOSSAVE CMOSREST and CMOSCHK are shareware. If you like them send
$20 US or Canadian to:

CMOSSAVE
Canadian Mind Products
#168 - 1020 Mainland Street
Vancouver BC Canada
V6B 2T4
(604) 684-6529 voice
(604) 684-5541 fax

We can take Visa, but not other credit cards by phone.

Please mention the program title since we sell thousands of
different products.

We in return will send you the latest version complete with MASM
source for CMOSSAVE, CMOSREST, CMOSCHK, REBOOT, BOOTSAVE,
BOOTREST and BOOTCHK.

If you don't register, we will not do anything mean to you. We
don't even want you to feel guilty. This is fee is purely
voluntary. Enjoy.

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