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I have a Lenovo Thinkpad Carbon X1 which has started to misbehave recently. The basic symptoms are that it

  • Can't be relied upon to start when pressing the power button (not sure if it never does, or if it just mostly doesn't)
  • Usually starts by itself if I plug in the power coord when it's turned off (again, can't be sure if this always happens or just mostly)
  • Displays the following message upon startup:

System CMOS Checksum Bad - Default settings used
Real Time Clock Error - check time and date settings

Pres F1 to edit settings, or Esc to continue

If I press F1 and change the date in BIOS to something remotely reasonable (usually I just change the year to 2015 and leave the rest unchanged) it reboots twice when I hit F10 for save and exit, and then starts normally.

If I press Esc, I'm presented with the same message, minus the first row (i.e. only the real-time clock error). I can then either change the date (as above) or press Esc again, and have the computer reboot again and then start normally.

I have fiddled with the BIOS settings, because I'm dual-booting Windows 8 and Ubuntu 14.04, and to make it boot into GRUB2 rather than the Windows Boot Manager, I had to change some settings related to UEFI/Legacy boot. I had this working for the better part of the past fall, but all my settings were reset when Lenovo pushed a BIOS update a couple of weeks ago so I had to re-fiddle. I can't remember if I had seen this behavior before or after that (yes, I really should have asked this question immediately instead of fiddling around to see if I could fix it...)

The symptoms show up regardless of, and are from what I can tell unaffected by, which OS I booted last.

If there is any other information I can get that would be helpful, please ask in the comments. I don't know enough of this to know exactly what is relevant, or how to troubleshoot (more than trial-and-error, which hasn't worked so far...).

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1 Answer 1

Reset to default
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That sounds like your CMOS battery is dead. This problem should be completely resolved simply by replacing the cmos battery.

I think this because of the messages you get on startup. The behavior is weird, but then again, I've seen dead CMOS batteries do the strangest things (like preventing a computer from shutting down)

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  • OK. Does this mean I need to send the laptop to a repair workshop? (Or can I somehow "revive" the battery without having to open the casing?)
    – Tomas Aschan
    Commented Feb 19, 2015 at 9:15
  • Also, is there anything I can do to verify if this is indeed the case?
    – Tomas Aschan
    Commented Feb 19, 2015 at 9:16
  • if you don't feel comfortable opening up your laptop, then yes. However, it should be fairly simple to do. You'll need to buy a CR2032 watch battery, which should be available in local stores. Then, you will open the panel on the bottom of your laptop and see where the old battery is. You'll just have to pop it out, and pop the new one in.
    – Blaine
    Commented Feb 19, 2015 at 9:17
  • 1
    Thanks for all the follow-up! I tried shutting down, keeping the power chord plugged and turning on again, but the machine didn't respond to the power button; the only way I could get it to start up was to unplug and re-insert the chord, but then of course I couldn't test booting without removing the power chord... I have filed a support request with Lenovo, to see if I can fix this myself without voiding the warranty of the laptop, or if I have to send it in. Thanks again!
    – Tomas Aschan
    Commented Feb 19, 2015 at 10:35
  • 1
    Fun fact: the repair dude arrived today, dug his way into the guts of the machine, and surprisedly exclaimed "hey, there is no CMOS battery in here!" In other words, good catch :)
    – Tomas Aschan
    Commented Feb 20, 2015 at 13:38

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