# [SOLVED] CMOS Checksum Bad



## Matteus

Hi,

My computer is giving this error in the BIOS: CMOS Checksum Bad.

I tried replacing the CMOS battery with a new one but it didn't solve the problem. Apart from that the PC is turning on automatically when I switch on the mains plug and the time and date are not being set correctly.

I was thinking of doing a BIOS Update. Will that solve the issue? How can I do the BIOS update?

Thanks.


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## DBCooper

*Re: CMOS Checksum Bad*

Hi Matteus,

First thing please post your compute specs including the brand/model of your motherboard. Hope everything works out well for you.


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## Tyree

*Re: CMOS Checksum Bad*

It is highly doubtful thata Bios update would resolve your problem.
PC Specs?
Prebuilt- Brand Name & Model Number
Custom Build- Brand & Model of Mobo-CPU-RAM-Graphics-PSU


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## Matteus

*Re: CMOS Checksum Bad*

Custom Built:
Motherboard - ASRock ALiveNF6G-VSTA
CPU - AMD Sempron 3000+
RAM - 2GB DDR2 800MHz
HD - 250GB Western Digital


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## Wrench97

*Re: CMOS Checksum Bad*

Does it continue to boot or hang after posting that message?

See if the battery voltage is listed in the bios on the hardware health page(if it is in fact posting)


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## Matteus

*Re: CMOS Checksum Bad*

The computer hangs at that error. In order to continue booting one will need to press "F1" button.


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## Wrench97

*Re: CMOS Checksum Bad*

But can you press F1 and continue or not?


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## Matteus

*Re: CMOS Checksum Bad*

Yes of course, I press the F1 button and the PC boots into Windows.


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## Wrench97

*Re: CMOS Checksum Bad*

Check in the Bios on the PC health page to see what the battery voltage reading is.


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## Matteus

*Re: CMOS Checksum Bad*

to be honest when i went in the bios, I couldn't even find the battery voltage


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## Wrench97

*Re: CMOS Checksum Bad*

Your right that board does not have a battery reading in the bios, it's usually a battery problem when it continues to boot after that message, when you changed the battery did you enter the bios and save optimal defaults on the exit page?


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## Matteus

*Re: CMOS Checksum Bad*

Yes I did save optimal defaults before exit of the bios. Even if I go now in the bios and save date and time, it will only save them untill I shut down the computer and remove the mains plug.


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## Wrench97

*Re: CMOS Checksum Bad*

It's usually a battery or connection issue in the battery socket did the 2 contacts look ok when you had the battery out?


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## Matteus

*Re: CMOS Checksum Bad*

Yes everything looked fine, at first it was not doing this error, it just didn't keep the date and time saved. But after a while it started showing this error.


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## Wrench97

*Re: CMOS Checksum Bad*

Both are related to the bios rom chip losing it's memory, the battery powers the chip in order for it to retain date/time and optional settings, Make sure the Clear CMOS jumper cap is correctly positioned on pins 1&2 of the header.
It's labeled CLRCMOS1 right next to the battery, pin 1 is closest to the battery.


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## Matteus

*Re: CMOS Checksum Bad*

The jumper is correctly set on pins 1 and 2.

Is there anything more that could be checked?


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## dai

*Re: CMOS Checksum Bad*

the most common cause of the error is a underpowered system


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## Matteus

*Re: CMOS Checksum Bad*

Underpowered system? I have a 400W PSU installed on this machine. It doesn't have anything special, an AMD Sempron Processor and 2gb of DDR2 Memory.

I've built i3 systems with a smaller PSU so I don't think that a 400w psu has to do that problem.


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## dai

*Re: CMOS Checksum Bad*

it is a pcie system it is underpowered

no 400w is going to have enough amps available for use amp output on the 12v line


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## Matteus

*Re: CMOS Checksum Bad*

i am understanding. can you please specify?


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## dai

*Re: CMOS Checksum Bad*

to run reliably you need to see a min of 40a listed on the 12v+ line for pcie

you will not find that on a 400w psu


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## Wrench97

*Re: CMOS Checksum Bad*

What are you using for Video, The integrated on the motherboard or a PCIe x16 Video Card?


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## Matteus

*Re: CMOS Checksum Bad*

i can't understand what you mean. can you please tell me?

I am using on board graphics. The pc wasn't doing this error before, it just started doing it now.


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## Wrench97

*Re: CMOS Checksum Bad*

Did you ever change the coin cell battery on the motherboard?


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## Matteus

*Re: CMOS Checksum Bad*

yes i have changed it because the time was not being saved but no there was no difference. The same error kept popping out.


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## Wrench97

*Re: CMOS Checksum Bad*

Did this start before or after the battery change?


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## Matteus

*Re: CMOS Checksum Bad*

it started showing that the clock is not good. then i changed the battery and now after 3 months or more it started showing also this error. 

Does it make a difference if it occurred before or after?


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## Wrench97

*Re: CMOS Checksum Bad*

Only if it occurred immediately afterwards.

For the price of a battery I would try another one first before doing anything else.


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## Matteus

*Re: CMOS Checksum Bad*

changed battery again as you told me and everything is working fine. thanks!


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## Wrench97

Good to hear that resolved it, hopefully it was just a bad replacement battery the first time around.


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