CMOS checksum

NTDEV
1

Hi all !

I am looking for a way to set bios password from my driver by writing to
CMOS (using ports 0x70,0x71).

I can encrypt/decrypt the passwords of most bios types, but the problem is
that I don’t know how to calculate the

checksum, that should be changed when the password is changed.

I would appreciate if somebody can give any info or references on the
checksum calculation algorithms for CMOSes.

Thanks,

Dani

2

I used to work as a BIOS engineer.
Regarding your questions, there are two problems:
First, nowadays chipsets use more than ports 0x70/0x71 to store CMOS registers. They are called extened cmos registers, and the way to access them is chipset dependent.
Second, what CMOS registers should be caculated into checksum is hardware dependent. The best way to find out is to ask the bios engineer. ;p

Regards,
Peter.

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com]On Behalf Of Dani Polovets
Sent: Monday, May 22, 2006 8:26 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] CMOS checksum

Hi all !

I am looking for a way to set bios password from my driver by writing to CMOS (using ports 0x70,0x71).

I can encrypt/decrypt the passwords of most bios types, but the problem is that I don’t know how to calculate the

checksum, that should be changed when the password is changed.

I would appreciate if somebody can give any info or references on the checksum calculation algorithms for CMOSes.

Thanks,

Dani

Questions? First check the Kernel Driver FAQ at http://www.osronline.com/article.cfm?id=256

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3

> I am looking for a way to set bios password from my driver by writing to

CMOS (using ports 0x70,0x71).

Are you sure that BIOS setup storage is still on these ports on modern ACPI
machines?

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

4

Some of them use CMOS only, but most new BIOSes use the eeprom in addition.

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Maxim S. Shatskih
Sent: ? 22 ??? 2006 19:11
To: Windows System Software Devs Interest List
Subject: Re: [ntdev] CMOS checksum

I am looking for a way to set bios password from my driver by writing to
CMOS (using ports 0x70,0x71).

Are you sure that BIOS setup storage is still on these ports on modern ACPI
machines?

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

To unsubscribe, visit the List Server section of OSR Online at
http://www.osronline.com/page.cfm?name=ListServer