Whats the difference between clear cmos and removing the battery?

robfosters · 1 Jul 2019 at 19:30

I overclocked my memory and got a black screen, no post. I cleared CMOS using the clear cmos button on the back of my AS Rock Z68 board. Did it three times to no avail.

Today, I opened the case, and removed the battery on the board for 2 minutes and put it back. Booted straight up to default values.

Why did removing the battery work, but clearing CMOS using the dedicated button do absolutely zilch? What's the difference?

azazl187 · 1 Jul 2019 at 19:31

You mean with over 28000 posts you have never asked this question before!?

I'm disappointed with you.

Did you press and hold the clear cmos button for 5 to 10 seconds?

robfosters · 1 Jul 2019 at 19:38

azazl187 said:
You mean with over 28000 posts you have never asked this question before!?

I'm disappointed with you.

Did you press and hold the clear cmos button for 5 to 10 seconds?

Yep. Computer went to reboot but wouldn’t post.

azazl187 · 1 Jul 2019 at 19:42

Maybe the memory overclock screwed the system so much even the clear cmos button couldnt save you.

Have you tried since. Maybe chance something really small that you know won't affect the system and then try again.

LuckyBenski · 1 Jul 2019 at 20:03

My reasoning is this: if the PSU is on, the motherboard has 3.3V so isn't using the battery.

If the battery is still in, clearing CMOS might be fighting the battery backup.

So removing the battery and switching off the PSU leaves the CMOS on its own -> that's when the jumper/button will surely work.

robfosters · 1 Jul 2019 at 20:41

LuckyBenski said:
My reasoning is this: if the PSU is on, the motherboard has 3.3V so isn't using the battery.

If the battery is still in, clearing CMOS might be fighting the battery backup.

So removing the battery and switching off the PSU leaves the CMOS on its own -> that's when the jumper/button will surely work.

But that would clear the CMOS anyway, so you wouldn't even need a button.

LuckyBenski · 1 Jul 2019 at 20:43

robfosters said:
But that would clear the CMOS anyway, so you wouldn't even need a button.

But how quickly? The storage work is done by capacitance. So it will hold charge if you don't short it.

clone · 2 Jul 2019 at 08:40

I always take the battery out when installing a new bios even though I've got a button on my motherboard.

edscdk · 2 Jul 2019 at 08:47

unplug from mains, remove battery wait 5 mins put some jam under battery, insert battery defecate in case,

I never usually wait 5 mins more like 2 seconds but it might make a difference some times,

(some of the steps listed above are not really necessary)

clone · 2 Jul 2019 at 08:49

To late I've done what you said so what now