Power cuts causing BIOS settings to be changed

  notnef 16:35 11 Jul 2010

After recent power cuts,when I boot up my PC, the BIOS settings are automatically changed back to those I used 18 months ago before an additional hard drive was installed

I have succeeded in resetting the correct ones which is a pain, ( by resetting the IDE Hard drive option) but I want to know why this happens and what I can do to prevent this happening.

I have a TRUST UPS 1000 and PC uses Windows XP SP3. Would a surge protector help?

Thanks for any helpful suggestions

  ashdav 16:43 11 Jul 2010

Mobo battery needs replacing.

  notnef 16:53 11 Jul 2010

sounds like a simple solution but still interested why a power cut would cause this- normally on boot up, there are no problems

  northumbria61 17:15 11 Jul 2010
  northumbria61 17:16 11 Jul 2010

Often, a dying battery will first manifest itself intermittently. Sometimes, you will boot with no problem. At other times, you will see an error indicating that the system doesn't match the configuration.

  ashdav 22:18 11 Jul 2010

Computer will retain settings until the mains is removed.
The battery is there for backup.
No mains and dud battery means the bios reset to default.

  Dark Mantis 08:10 12 Jul 2010

He says that he is using a UPS so the fact that the mains was cut shouldn't have made any differnce also with or without amins supply the batttery on the motherboard wouldn't have made any difference. If it was gone the result would be the same as soon as he shuit the machine down.

I would think that you probably hjad a spike in the supply as it returned. This would be fairly normal. Your Trust UPS should have filtered that out but they are not as good quality as APC or the like.

  ashdav 08:26 12 Jul 2010

Dark Mantis
UPS are not infallible.Depends on what type it is.
If it cuts in when the mains drops out then there can be a delay.
If it's always online then it's better but these are not cheap or small.
Mobo (including CMOS) is powered by the mains even when the computer is shut down. The CMOS is kept powered by the 5v supply. The battery is also connected via a Schottky diode (low voltage drop) so that the CMOS receives a supply if the mains disappears.The diode stops the battery being "charged" when the 5v supply is present.

  Dark Mantis 10:30 12 Jul 2010

Thanks for explaining all that complicated stuff to me. You are quite right about the good quality UPS not being cheap although I wouldn't say that the size was an issue. I run a APC 1500 Smart UPS and it has only the footp[rint of a small computer and is only about 8" (20cm) high. I was in fact talking about line-interactive UPS systems and that was my point. If you turn off your UPS unit when you shut down your computer then there is no standing supply to the machine any more. Besides that standard Litium 2032 cells as are used in motherboards nowadays are non rechargeable.

  ashdav 10:37 12 Jul 2010

That's why I put "charged" (being tongue in cheek).

  notnef 10:53 12 Jul 2010

your answers are very illuminating and I realise how little I know ! Nothing is that simple

2 extra points

When the power goes off should I disconnect the UPS from the power point ? What is the sequence I should follow when the power gets restored?

Should I go buy a surge protector ? Any recommendations (PC, Printer, Netgear wifi modem and monitor + UPS)

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