CMOS Data Storage Location

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CMOS Data Storage Location

Postby seekermeister » Thu Sep 10, 2009 11:57 am

I just installed a used A8N32-SLI Deluxe MB that I bought, and on boot it say that there is a bad CMOS checksum error. I have tried every means known to me to correct this, without any luck. Therefore I got to wondering if the CMOS data is contained in the BIOS chip or elsewhere?

The BIOS version (703) currently installed is quite dated (11/04/2005), so I thought it would be worth a shot to flash the BIOS, but I have nearly no experience with that, and would probably replace the chip instead...if that would likely solve the problem...yes/no?
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Postby rascard2007 » Thu Sep 10, 2009 1:02 pm

normally it happens when the CMOS loses the stored information about ur settings. try replacing the MOBO battery, clear the CMOS before installing the new battery and enter to the BIOS setup to properly configure ur settings.

good luck
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Postby seekermeister » Thu Sep 10, 2009 1:50 pm

Thanks, but I understand about the normal solutions for this kind of problem, but they don't work. Therefore my original question stands.
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Postby fussnfeathers » Thu Sep 10, 2009 6:13 pm

Kinda hard to see, given the images I can find, but it appears that your board still uses two chips, one socketed chip for the BIOS (bottom right corner, yellow label with the initial BIOS revision stamped on it), and what I believe to be the CMOS chip soldered directly to the board next to it, to the left. Pretty much a typical config for Asus. Flashing the BIOS isn't exactly an option, if you're getting a CMOS error. You aren't getting anywhere near the point where flashing is possible. AFAIK, a checksum error on the CMOS indicates a bad chip.

Note that I think that's the CMOS chip, I can't find a zoomable picture to actually get a close look at it, but it appears to be. Try dropping an email to Asus, see what they say. It's entirely possible that I'm wrong.

*edit* Did a bit more digging. I was wrong. PDT_Armataz_01_03

The CMOS on your board is indeed on the same chip as the BIOS, and is replacable, but good luck finding one, that's a rather old board.
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Postby seekermeister » Thu Sep 10, 2009 6:24 pm

Thanks, that's what I needed to know. It doesn't appear to be a problem buying a chip, the Bios Depot and others are running ads on eBay for them.
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Postby fussnfeathers » Thu Sep 10, 2009 6:31 pm

Good to go, then. 8)
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Postby Karlsweldt » Fri Sep 11, 2009 1:15 pm

"CMOS checksum" is a general error message that something doesn't match with how the BIOS pages are set, to the physical association of the mobo. Could be the wrong date/time to duplication of devices or wrong memory or CPU not recognized. Or a USB keyboard not active, no default PS2 type found.
Most newer mobo types have either a single or dual BIOS chips. They have internal memory of up to 4 megs! The much older type of mobo would have used two large DIPP chips, about the size of a domino chip!
If the BIOS chip is in a socket, then it can be swapped. BUT if soldered to the mobo, forget it. If you intend to swap BIOS chips, ensure you get a guaranteed-to-work chip for that board.. or the board and/or the chip can become DOA.
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Postby seekermeister » Fri Sep 11, 2009 1:46 pm

All good to know, but I think that hardware compatability or detection problems can be ruled out, because the MB is the only component that I haven't used before, but I have been using an A8N-SLI without any problems at all. The BIOS connector is socketed, and the chip is new and guaranteed, so it should take care of things.
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Postby Karlsweldt » Sun Sep 13, 2009 6:43 am

The BIOS chip is hard-written to work with a specific chipset.. such as Intel, SiS, Via or VLSI for examples. But the user-configurable settings may be otherwise identical between models. Yet the BIOS chip will work only with that specific chipset type. And if the same chipset type is older or newer than what the BIOS chip was hard-written for, then problems also can arise. Certain device cards may require a "shadow" memory assignment, which may not be properly assigned automatically. A manual setting may resolve this issue.
Some success has been had with flashing one BIOS type to another, as long as it is in the same chipset family. But success is not a guarantee if the chipset model is not compatible to the BIOS program.
The safest way to flash a BIOS is with a floppy disk which is formatted in FAT-12 format.. the only format the BIOS can read before the OS comes into operation. The only files you need are the basic boot routine, with no frills.. and the BIOS flash program.
If you cannot format a disk properly with a current OS, look to www.bootdisk.com/ for appropriate formatting/boot processes.
It is wise to always save the current program for the BIOS, so you can do an "unflash" if there are problems. Save the old program with the same name as the new, but use a tagname such as 'old' instead of 'bin'. After any BIOS flash, it is important to ensure the old settings are obliterated. This can only be done by pulling the power plug from the PSU, attempting a few starts to drain reserves, then removing the battery and using the CLRCMOS jumper for a few seconds. After the routine, power up and go directly into all BIOS pages to reflect the true setup.
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