Clearing a BIOS can be done in two ways; the first is fairly simple, the second requires some hardware knowledge and skills.

The first method just involves entering the BIOS by the method required for that particular machine.  Pressing the DEL key on bootup usually does it but some machines vary.  After that, select 'Reset to Default' or whatever command seems to indicate that the BIOS will be reset to it's beginning configuration.  Then SAVE the setting and reboot.

However, it may be necessary to re-enter the BIOS again and change individual settings such as enabling ONBOARD LAN etc, which may have been previously customized.

The other method involves turning off the PC and opening the case.  Disconnect the power lead completely.
The BIOS settings are held in a little chip, referred to as a CMOS (complementary metal-oxide semiconductor) chip.

'Shorting out' this chip clears it of earlier information. You'll need the motherboard manual to ascertain which pins need to be 'shorted', which is done by connecting them for about 20 seconds with a 'jumper'.

The pins may be in a group of two or three and the cluster will be marked with something like 'CLR CMOS'.  There may be a jumper on the pins already, in which case it will probably be connecting the two that DON'T short it out, eg pins 1 and 2.  But using the jumper to connect pins 2 and 3 will effect the shorting process.

If it's a 2-pin set, there may either be no jumper or it'll be connected to one pin only (to locate it).

On some motherboards, there are NO pins, only two little solder blobs.  These can be shorted with a suitably bent paper clip.

You could also remove the CMOS battery (usually a shiny round battery about 3/4 inch across) and leave it out for 4-5 hours, which will slowly drain the CMOS of it's charge and settings.  Or, again with the battery removed, use a straightened paper clip to short out the battery terminals for about 20 seconds.

The CMOS battery and pins, will, on most motherboards, be found at the opposite end from the CPU.

Ian Porter
Computer Guys Inc.
Arrowtown
New Zealand
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The NOSPIN Group
http://freepctech.com

  ----- Original Message ----- 
  From: Ariel Torres 
  Subject: [PCBUILD] clearing bios


  Can you tell me how to clear the bios and reset it please I've never done it before and it was recommended by one of you. It seems that the hardrive will not boot. I installed it alongside my harddrive in my pc as slave and it worked fine, I could access all the files and everything in that harddrive but when I put it back in its pc it does not boot. I can even get into CMOS for a few seconds before it just locks up on me and then I have to hard boot it.

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