Whats the difference between clear cmos and removing the battery?

[robfosters]

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?

 

[robfosters]

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.

 

[robfosters]

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.