What is a "cmos checksum bad" error?

Question

Two days back when I booted my system up, it was showing a screen with a bunch of messages and instructed to press F12 to continue booting.

Two times it showed up when I booted my system and now it is not there, the problem was solved before I could take a screenshot of the message.

The only thing important I remember of the message is "CMOS checksum bad"

What is this error and how does it occur? How did this problem fix itself? (there wasn't any hardware changes at that time.)

If this problem persists in the future how can I go around without pressing F12 key.

score 3 · Accepted Answer · edited Jan 09 '14 at 20:33

3

Your CMOS battery is dead, put in a new one.

image of a CMOS battery

edited Jan 09 '14 at 20:33

Jawa

answered Aug 30 '13 at 15:17

Hardy

1

but the error doesn'nt persist.now itsseems okay. – Ashildr Aug 30 '13 at 15:19
2

if your un-plug your power cord, i guess you will see that message again – Hardy Aug 30 '13 at 15:20
1

@DEFCON1 Hardy is right, your power supply gives your motherboard a constant 5V standby voltage which keeps some of the electronics alive even when the machine is off so it could well keep the CMOS alive. When you have a power outage this 5V goes away, the battery is dead so can't keep the CMOS alive and the result is the error you see. – Mokubai Aug 30 '13 at 15:25
@DEFCON1 the reason that everything is alright after this kind of error is because pressing `F12` tells it to use a default set of options which while possibly not as optimised are perfectly good for 99% of systems. – Mokubai Aug 30 '13 at 15:30
@Mokubai , i have removed and reconnected my power cord.after these two times i have never experienced the "cmos checksum bad” error. – Ashildr Aug 30 '13 at 15:58
It might be that the battery can keep the CMOS going for some short period of time, but not long enough. Try it for an hour or a day or so and see if it still happens. Unplugging the lead for 10 seconds will not allow the capacitors in the PSU to fully discharge so will be enough to keep the CMOS alive as well. – Mokubai Aug 30 '13 at 16:07

1 Answers1