[OpenBIOS] PC-CMOS memory..

[David Christensen]

The de-facto standard for most south bridges is to use 0x72 and 0x73, some
will even use 0x74 and 0x75.  You'll need to check that the PIIX4 has the
second bank of CMOS enabled and unlocked but otherwise it's fairly straight
forward.  And you don't have to worry about bit 7 like you do when accessing
0x70 and 0x71.

Dave

-----Original Message-----
From: owner-openbios at elvis.informatik.uni-freiburg.de
[mailto:owner-openbios at elvis.informatik.uni-freiburg.de]On Behalf Of
Stefan Reinauer
Sent: Thursday, February 10, 2000 7:32 AM
To: openbios at elvis.informatik.uni-freiburg.de
Subject: RE: [OpenBIOS] PC-CMOS memory..


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Hi Dave,

> 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
> vendors.

Is there a secure way to access anything in the CMOS over 128 bytes? I wrote
some patches for the Linux nvram driver a long time ago to access not only
,64
bytes, but 128 bytes.
I read somewhere that everything over 128 bytes has to be accessed over
io registers 0x72 and 0x73 instead of 0x70 and 0x71. Has anyone information
on
that issue?


Regards,
     Stefan

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