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@elvis.informatik.uni-freiburg.de [mailto:owner-openbios@elvis.informatik.uni-freiburg.de]On Behalf Of Stefan Reinauer Sent: Thursday, February 10, 2000 7:32 AM To: openbios@elvis.informatik.uni-freiburg.de Subject: RE: [OpenBIOS] PC-CMOS memory..
-----BEGIN PGP SIGNED MESSAGE-----
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
- To unsubscribe: send mail to majordomo@freiburg.linux.de with 'unsubscribe openbios' in the body of the message
- To unsubscribe: send mail to majordomo@freiburg.linux.de with 'unsubscribe openbios' in the body of the message