Resetting CMOS Settings

Hi folks,

A few 'noob' questions about CMOS settings (desktop pc - specifically DELL Vostro 200 / Foxconn G33M02 motherboard).

To clear the CMOS settings you can take the CR2032 backup battery out (for several hours) or short out the 'Clear CMOS' jumpers on the motherboard.

Is one method better than the other?

If you use the jumper method, do you leave the power cord plugged in with the PSU switched off (so the pc is still grounded) or do you remove the power cord altogether (I have seen both options stated so unsure).

Secondly, if you use the jumper method, do you leave the CR2032 backup battery IN or do you take it OUT before shorting the 'Clear CMOS' pins?

The manual seems to suggest you simply short out pins 1&2 with a jumper - it makes no mention of the power cord or CMOS backup battery.

Thanks

Art

ArthurDent said:

Hi folks,

A few 'noob' questions about CMOS settings (desktop pc - specifically DELL Vostro 200 / Foxconn G33M02 motherboard).

To clear the CMOS settings you can take the CR2032 backup battery out (for several hours) or short out the 'Clear CMOS' jumpers on the motherboard.

Is one method better than the other?

If you use the jumper method, do you leave the power cord plugged in with the PSU switched off (so the pc is still grounded) or do you remove the power cord altogether (I have seen both options stated so unsure).

Secondly, if you use the jumper method, do you leave the CR2032 backup battery IN or do you take it OUT before shorting the 'Clear CMOS' pins?

The manual seems to suggest you simply short out pins 1&2 with a jumper - it makes no mention of the power cord or CMOS backup battery.

Thanks

Art

The "jumper" takes the place of removing the CMOS battery by temporarily shorting the battery to ground.

Also, you don't have to leave the CMOS battery out for a few hours.
With the PSU plugged in but switched OFF... hold the case power button down for about 5-10 seconds to discharge the capacitors. THEN when you pull the CMOS battery, you only have to leave it out for a few minutes.

How to clear the CMOS

Ghot said:

The "jumper" takes the place of removing the CMOS battery by temporarily shorting the battery to ground.

Also, you don't have to leave the CMOS battery out for a few hours.
With the PSU plugged in but switched OFF... hold the case power button down for about 5-10 seconds to discharge the capacitors. THEN when you pull the CMOS battery, you only have to leave it out for a few minutes.

How to clear the CMOS

Thanks GHOT. I thought that shorting the pins was the same as removing the battery but just as well to check

Highlight: Also known as 'Static Discharge'?

Art

ArthurDent said:

Thanks GHOT. I thought that shorting the pins was the same as removing the battery but just as well to check

Highlight: Also known as 'Static Discharge'?

Art

The static discharge arm bands and such, are for discharging the static electricity in your body, before touching electronic components. Especially in the winter.

Holding the case power button down with the PSU switched OFF... discharges the capacitors in the power supply and on the motherboard. To clear the CMOS you need to (one way or the other), remove all power sources for the BIOS chip, so it forgets all the settings.

Remember to always check the date/time in the BIOS after resetting it. Make sure it's correct.



You should also have an option IN the BIOS to reset to Optimized Defaults.

Ghot said:

The static discharge arm bands and such, are for discharging the static electricity in your body, before touching electronic components. Especially in the winter.

Holding the case power button down with the PSU switched OFF... discharges the capacitors in the power supply and on the motherboard. To clear the CMOS you need to (one way or the other), remove all power sources for the BIOS chip, so it forgets all the settings.

Remember to always check the date/time in the BIOS after resetting it. Make sure it's correct.

You should also have an option IN the BIOS to reset to Optimized Defaults.

Years ago (around 20) I used to work in PC Support and we called taking all of the leads out of the pc and holding down the power button for 30 sec (that's what we advised customers who were doing this themselves) to discharge the static from the machine which was preventing it from booting (on reflection, this seems to be discharging any capacitors of the mobo).

I am aware of static wrist straps and the perils of nylon/polyester carpet - especially in warm, dry rooms and the potential (pun intended) to fritz ICs.

Helmut said:

No need for any of that jumper lead stuff, check battery voltage and put in a new one if required, or if more than 5 years old.

You can just go thru all the BIOS/UEFI settings and select the defaults and Save > Restart. There maybe a defaults selection in the BIOS/UEFI, on mine it is, Set Defaults > Save and Exit.

If the settings battery has died the settings would have gone back to safe defaults anyway.

Hi Helmut,

The issue wasn't a low voltage on the CMOS battery, rather how to clear CMOS settings which was preventng the pc from getting any further than the BIOS 'Splash' screen (F2/F12 and booting from USB or CDROM wasn't possible as the machine wasn't getting that far).

All sorted now (at least on gettin the pc into BIOS Setup / Windows / Linux Mint - but not as to resolving the 'jiggling cursor' which is the subject of a different thread < here >. There are three short video clips in my latest post in that thread showing the behaviour in BIOS setup, Windows and Linux Mint.

That has me really stumped as the 'jiggling cursor' appears in Windows (booting off a Win 10 SSD, Win 10 HDD or Win 7 HDD) or off a bootable USB thumb drive with Linux Mint on it, but not on the BIOS setup screen (no mouse cursor). Changing the mouse from a wireless Logitech to a wired mouse (still using USB to connect) makes no difference nor does changing the motherboard and CPU combo - as I said, this has me really stumped.

I've swapped out various RAM modules in and out, disconnected the CDROM, disconnected the front-panel multi-card reader and used the on-board graphics (after removing the PCIx Graphics Card) and the 'jiggling cursor remains'.

I'm beginning to suspect some Voodoo!

Art

Watch the voltage level on those CR2032 batteries. My previous Gigabyte board failed to boot when the open circuit voltage was below 3V. These batteries also rapidly lose voltage at the end of their life. You only need to remove the battery for a minute or so to reset the CMOS. It's good practice to also load the BIOS defaults.

Steve C said:

Watch the voltage level on those CR2032 batteries. My previous Gigabyte board failed to boot when the open circuit voltage was below 3V. These batteries also rapidly lose voltage at the end of their life. You only need to remove the battery for a minute or so to reset the CMOS. It's good practice to also load the BIOS defaults.

Hi Steve,

Thanks. Measured it with a DMM yesterday and the o/c voltage was 2.99V

Art

ArthurDent said:

Hi Steve,

Thanks. Measured it with a DMM yesterday and the o/c voltage was 2.99V

Art

That's marginal so would use a new battery which should be 3.2V +

Steve C said:

That's marginal so would use a new battery which should be 3.2V +

Art