[OpenBIOS] PC-CMOS memory..

David Christensen dchrist at home.com
Mon Jan 10 08:57:19 CET 2000


The short answer is no, you can't use this memory.  The PC BIOS assumes
exclusive ownership of this hardware.  Unless you want to go to the effort
of mapping the CMOS usage for a particular platform (which is complicated by
the fact that some BIOS vendors rearrange their CMOS usage between each
version of their ROM!).  You may find that some hardware platforms have
totally unused CMOS (for example, the PIIX4 has 256 bytes of CMOS, but many
platforms will only use the first 128 bytes) which you can take advantage of
but this is a hardware specific implementation and varies between platform

As to what is stored there, there are obvious things such as the date and
time, disk drive parameters, and most every setup option is stored in CMOS.
The BIOS may also use CMOS during POST for temporary storage, or it may
store hidden setup values that you can't change in setup, or just about
anything else for that matter.

David Christensen

-----Original Message-----
From: owner-openbios at elvis.informatik.uni-freiburg.de
[mailto:owner-openbios at elvis.informatik.uni-freiburg.de]On Behalf Of
Janusz J. Mlodzianowski
Sent: Monday, January 10, 2000 3:47 AM
To: OpenBios
Subject: [OpenBIOS] PC-CMOS memory..

Hi to all in Open Bios project,

My question is not directly (yet..) related to OpenBios project but I do
to find here an answer.
I am writing an embedded PC application project in which I would like
to use some of PC CMOS memory. All documentation I have found does not
seem to be correct. Especially in the area of HDD data (types 47,48).
Each motherboard I have tested seems to store this data in different
Configuration data is stored in the first 64 bytes. RTC memory consists
of 128 (or more locations). What is stored there. Can I safely use this
for my own purposes?

Thanks for comments.

To unsubscribe: send mail to majordomo at freiburg.linux.de
with 'unsubscribe openbios' in the body of the message

To unsubscribe: send mail to majordomo at freiburg.linux.de
with 'unsubscribe openbios' in the body of the message

More information about the openbios mailing list