Dead processor chip and BIOS

[Emirzan]

I've not actually had a processor chip die on me before and may be in that situation now. Sadly I have no other to swap in its place (it's an old machine and I have no other socket 478 chip available) so I'm trying to figure out if I can run any sort of test.

First a question I hope someone here can answer, would a motherboard with everything else in place still be able to post with a dead cpu? Or does the processor need to be active for the bios to run the boards self test?

Secondly, will a dead processor result in a hardware fail post code from the board or will there be no indication at all? I can't seem to find anything useful on the web at the moment.

Before anyone asks, yes, cooler checked, remounted, power supply checked, ram checked etc. And all double checked for good measure

[Agent]

1)Processor is required for POST no way to run tests without it.

2)Depends on the motherboard. Some will give you a beep / POST error code. Others will just sit in silence laughing at you
Abits will display the POST error on its LED display

[Emirzan]

Thanks Agent, so if I'm able to get any POST codes at all that would indicate the chip is healthy?

For example forcing the 'memory not detected' code by taking the RAM out, which does give the relevant code in this case. As for LED post readouts, this is a computer from way before those were introduced sadly. Currently sat in a room with 3 broken or part built desktops and 1 working laptop, great fun.

[Agent]

Thanks Agent, so if I'm able to get any POST codes at all that would indicate the chip is healthy?

Afraid its not that simple - you could be getting POST error codes with a faulty CPU. It purely depends on the motherboard.
What is the POST code sequence - where does it say the error is?

For example forcing the 'memory not detected' code by taking the RAM out, which does give the relevant code in this case. As for LED post readouts, this is a computer from way before those were introduced sadly. Currently sat in a room with 3 broken or part built desktops and 1 working laptop, great fun.

The only way you're going to be certain its the CPU is by swapping it out with a known working one
There is no easy way to tell if its the CPU or the motherboard that's broke for example.

In addition there is also the possibility that the RAM POST error comes before the one for the CPU - thus stops there and won't go any further.

[Emirzan]

Hmmm, thought it was too good to be true. I've been browsing the manual (took a while to find it) and there isn't actually a specific code listed for a cpu fail. Which makes me think it would probably display 'cpu not present' on the startup screen. Seeing as I can't get this far I still don't know the problem.

The computer in question is significantly old but functioned reasonably as an internet browsing machine for a family member. Financially it's probably not worth buying another 478 chip and possibly motherboard, looking on scan the only available chip is £100+. I think I might as well build a cheap new c2d system. From a personal interest point of view I'd like to know what's wrong with it but I guess it's not practical to find out

I'm actually quite amazed this computer has lasted as long as it did, opened it up and was greeted by a stunning amount of dust. And 2 rather loud high pitched 80mm fans to shift it all.

[Agent]

It's worth seeing if there is anyone in the For Sale forum who has one you can get for cheap. A old cellery shouldn't cost more than beer money
I don't think I have any 478's lying about, but I'll have a check.

What makes you suspect its the CPU though? It it usually the last thing to suspect if it was working fine previously You're right though, a basic c2d system is *cheap*....worryingly cheap to be honest.

[acrobat]

Theres also the possible option of trying the chip in a friend's PC too. Bit of a pain in the bum doing that though because you have to take the case lid off and then the heatsink and then have to do all that faffing around with the thermal paste removal and adding new thermal paste... bleh. It's an option though anyway.

And you could maybe even just put it in without applying new paste just to test it.

[Emirzan]

Not sure it is the processor, you're right, it is an unlikely thing to go wrong. I think it's much more likely that dust has clogged the motherboard and something has shorted/burned out. Be it a simple connection or one of the microchips. I was curious as to how I'd tell IF the processor was dead though, curious to know the relation of BIOS and processor too.

Don't worry about finding a chip Agent, thanks for looking though I get the impression that my aunt would prefer a new computer anyway and I'm happy to build one. This one is now pushing 6 years I think.

And you could maybe even just put it in without applying new paste just to test it.

Hmmm, I don't think I'm comfortable with that idea, I'd only have seconds before definitely destroying it! I don't actually know anyone else still running a 478 system I think. Not within easy travelling distance anyway. Trying it in another system would be the best test, it's a good thought but not really a viable option.

[acrobat]

Hmmm, I don't think I'm comfortable with that idea, I'd only have seconds before definitely destroying it!

I don't mean do it without the heatsink, I mean do it *with* the heatsink but without re-applying the thermal paste. You can leave the old paste on and as long as you don't touch it or get dirt in it, it should still make an ok connection between CPU and Heatsink. And all you would need to do is turn it on and see if it starts to boot. If it does, and if you can see the bios going through it's process, then you can just turn it off again. You should know whether it's working or not in no more than about 5 seconds, and I doubt the CPU will even get luke warm in that time.

[Emirzan]

Ah, gotcha. Yeah, I've done that before. Perfectly ok for a quick test in my experience. Misunderstood what you were describing in the previous post.

[acrobat]

No worrys, hope ya get it sorted. Let us know how you get on.

[peterb]

Not sure it is the processor, you're right, it is an unlikely thing to go wrong. I think it's much more likely that dust has clogged the motherboard and something has shorted/burned out. Be it a simple connection or one of the microchips. I was curious as to how I'd tell IF the processor was dead though, curious to know the relation of BIOS and processor too.

Unlikely to be dust causing a short.

Bsically, when you start the computer a timer chip holds the reset line on the processor in an asserted state until all the psu lines are stable. Once that has occured, the processor is allowed to start, and jumps to a prededined address (which is the entry point for the BIOS) and starts executing the code there. That code includes the POST routines - which therefore by definition are executed by the processor. (So unless there is a separate controller to test the CPU - you can't detect missing CPU - so no screen display)

So the problem in your case comes down to :

Faulty PSU or PSU connections
Faulty CPU (unlikely)
Faulty MOBO - in the area of the initial timer and/or associated Poer detect circuitry
Damaged BIOS

However, in an earlier post you did say that removing the RAM gave a beep code (or I mi-understood what you said) in which case either damaged RAM or problems with the memory controller. If it was the latter, I'd expect some form of error indication with or without RAM.

Without detailed knowledge of the MOBO layout and circuitry (and a lot of patience and test equipment) it would be difficult to pinpoint exactly what is happening - substitution is the only practical way - difficult when the components are obsolete.