Bios or Cpu failure how to tell

  No idea 11:59 10 Sep 2005

Hi, My system has crashed showing all the symptoms of bios failure, I was sure this was the problem and manged to find a suitable board on e-bay.However to my dismay computer still will not boot up ,with blank screen and no bios loading . I think that the only thing it could be is that my processor has given up the ghost .I do not have a replacement to hand so how can i tell short of buying another processor how to check? any suggestions welcome.I have checked using another computer that all other items i.e graphics card and hard drives are ok .

  Diemmess 12:16 10 Sep 2005

To me in a fanciful way I assue the BIOS to be a set of Standing Orders.

The CPU is a calculator and complex information exchange, which executes those standing orders to begin with and any other instructions pickeup as the boot goes on to the point of handling extra instructions as an application is loaded.

Normally when something goes wrong with the bios there will be bleeps and error messages galore.

Are you sure the PSU hasn't failed?

  Diemmess 12:19 10 Sep 2005

Atrocious spelling - should have checked

  No idea 12:22 10 Sep 2005

I have not been able to check, because short of trying replacement i do not know how to tell.I have not had any error or beep codes from the bios and the display monitor reports no signal this could also be a sign of processor failure?As I said i have replaceed entire board but symptons still persists

  Diemmess 13:21 10 Sep 2005

From a balance of probabilities between your motherboard with its BIOS, the CPU and the PSU, I would rate the PSU much the most likely to have failed.

Assuming that the fuse in the plug is OK there are all sorts of variations of failure, but the fact that you see and hear nothing after switch-on - points very strongly at the power supply unit.

Substitution is the only sure and safe way of checking but the good news is that the PSU is much much cheaper than mobo or CPU

  No idea 13:44 10 Sep 2005

to the motherboard because the neon light is on and also the hard drive lights come on.but system will not boot into bios so could cpu be at fault is substitution the only way of finding out?

  woodchip 13:47 10 Sep 2005

That does not mean a think with a Power supply. How much current do you think a motherboard etc take's compared with a little light

  No idea 19:24 10 Sep 2005

the neon light , however I can put a 15 watt or 500 watt light bulb in my household supply, they both tell me that particular circuit is working.Not being a electronic engineer perhaps you can tell me something that might be more pointing to the problem instead of a general remark.Obviously it is highly unlikely that two boards have the same fault,so the only thing I can do is substitute psu and cpu units.Any other helpful ideas welcome ,thankyou

  Gongoozler 20:05 10 Sep 2005

For the home user there is really no certain way of being certain whether the fault is in the motherboard or the processor other than by substitution. The equipment required to differentiate between the two would be very expensive. You can get a good idea if the PSU is working by measuring the volts on a spare 4-pin drive power connector with a multimeter. One outer pin should be +12V and the other should be +5V, both relative to either centre pin. If you don't have a multimeter you can get a suitable one for about £2.50 + £2.50 postage click here, although this one at £5 is better click here

  Dollybird 20:06 10 Sep 2005

My PC was showing different errors everytime I booted to, I to was suspecting CPU failure, but I
did notice a slight change in sound coming from my power supply. I then changed this for the cost of £15.00 - errors no more!!

  Diemmess 20:07 10 Sep 2005

A PSU in spite of its relatively low price is a very smart piece of kit.

It involves producing a smooth DC current supply and monitors the current drain to maintain the exact voltages on the power supply leads which plug into both the Mobo and any drives Hard or optical, as well as providing power for USB and other circuits.

There are several different voltages all maintained within very tight limits, but supplying different needs like the HD and Optical Drives or the different parts of the Mobo. Each circuit will have its own voltage regulator and so on.

It only takes one of these circuits to fail and the computer wont work.

Because the voltage monitoring depends on a complete circuit with a component it is no use trying to measure the available volts by just stuffing test prods into a plug which is carrying no load. Sometimes a voltage will be available under no-load conditions, but as soon as that circuit has a current demand the voltage will drop to zero or almost.

This is why, (given that power supply units do fail) the only safe way to check is to plug it into the computer first and then switch on. You may have an indicator lit showing something is happening, but that really doesn't prove much.

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