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C640/540 - EEPROM Wipe

By Nidox
Nov 18, 2007
  1. Hello.

    I have been reading the forums quite alot recently and discovered that if you short together two pins on the EEPROM chip you can reset the settings and clear passwords from the BIOS.

    I have been trying this method for quite some time with all the combinations of pins i can find but none seem to work, I have found the right chip using this picture.


    So I hope this is the right chip. :S

    Any advice on how to proceed would be greatly welcomed, I know that when I short the two pins and boot the PC the service tag on my 'dell', hiss boo, should be wiped but nothing changes.

    I'am beginning to suspect there is another deeper chip that stores this info aswell, possibly called NVRAM as I have heard it bounced around the forums before.

    Thanks in advance
  2. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,231   +234

    The "shorting" method doesn't work on all models. Are you sure you have the correct model for this to work? Did you remove the batteries (Main and CMOS)
  3. QuiescentWonder

    QuiescentWonder TS Rookie

    I know it's an old topic but I have personally done this on a C640 and it works. I can't remember which pins to short (it isn't what most people say for this NVRAM chip). Maybe 5 and 7, try combinations of the pins around those pins. It took me 15 minutes of trying different combinations but it does work.

    The chip is a ht24lc04, here is a picture.


    A Dell technician told me that you can short the same pins on the LPT port instead of on the chip itself. For example, pins 5 and 7 on the chip itself correspond to pins 5 and 7 on the LPT port, which is much easier because you don't have to take the laptop apart. I haven't tested this myself.
  4. dello

    dello TS Rookie

    I have just reset the bios password on a c640. it had the newer service tag ending and not the d35b service tag ending

    there was NO battery installed and the cmos battery was unplugged

    directly after switching the power button, i shorted out pins 5 +4 which are the two furthest away from dim slot 1. all the post I read everywhere suggest you short across pins 3 + 6 which are the penultimate furthest away from dim slot one, but this didn't work for me so I tried 5+4 and bingo.

    beware not to short pins 1+8 which are the legs closest to the dimm slot, as I think pin 8 in the power leg and I read you can stuff the laptop
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