In article <d4l2vf$bqd$1@inn.qnx.com>, evanh@clear.net.nz says…
ed1k wrote:
PC has additional unused CMOS bank, I know it from the month I bought it
almost 3 years ago >
Oh, I forgot to mention, I know how to write data to that part of CMOS
and read them back. But I din’t find any use of it so far >
Yeah, reading and writing is no problem, the problem is BIOS will reset the contents on the next boot up.
Nope. If you use CMOS bank which is in use by BIOS there is always a
danger to overwrite something important Of course, if you confident
that some bytes are not used by BIOS, you can use them, but you have to
recalculate CRC and write new CRC as well.
What I was talking about is external CMOS bank provided by some
chipsets, and sometimes it’s completely unused by BIOS. My IBM 300GL
uses both primary and external CMOS banks, but some Award modular BIOS v
4.51PC on my dual Pentium II SMP box doesn’t use it, for example. So, I
wrote a hex signature to external CMOS bank and it is still there for
years. If someone still my computer I’ll have a tip for the police
I didn’t find any use of it because it’s deeply hardware dependent. You
have to have RTC chip with extended capacity and BIOS that doesn’t use
it. Every chipset has a different rules to configuring access to it -
there is no single interface and seems nobody meant CMOS for application
layer. Nonetheless it would be a great asset especially for diskless
system, for example.
If you have some hardware around built on 430VX or 440 chipset you can
try small utility I attached. Just today I added support for 845GE
chipset (I hope I didn’t break anything)
First, you need a PC with 82371AB PIIX4 chip (VID=0x8086 DID=0x7110) or
with 82801DB ICH4 chip (VID=0x8086 DID=0x24C0). ‘pci -vv’ is your
friend.
Second, you need a BIOS on this PC that does not
use extended CMOS bank. Run
…/lscmos
and see if there are all 0xFFs in extended CMOS bank.
If you find a PC that meet two conditions above, run
…/lscmos -s
and again
…/lscmos
to confirm that signature is written to the first four bytes of the
extended CMOS bank.
Reboot you system. If BIOS didn’t complain about wrong
CMOS CRC, run ‘lscmos’ again to check the signature is
still there.
No easy way to remove the signature, except probably using
jumpers on motherboard If something went wrong and
your computer does not work anymore, it’s solely your
fault.
Cheers,
Eduard.
Attachment: lscmos 6309 bytes
begin 600 lscmos
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