[clue-tech] computer won't boot

[marcus hall]

On Thu, Nov 03, 2005 at 10:36:03AM -0700, Michael Mosbauer wrote:
> I had the same problem happen to one of my computers.  The fan would 
> come on, so I knew the PS was working, but I had no beeps nor other 
> indicators of anything working.  Reading the last post, it makes sense 
> the BIOS would be dead.  I replaced my motherboard (didn't think about 
> the BIOS) and my system has been up and working since. 

The BIOS is nothing more than a program that the processor runs after booting
up, stored in a (typically Flash) ROM.  Although it is possible that the
ROM chip itself can fail, the most likely failure of a BIOS is a failed
re-programming attempt.  But, unless there is reason to suspect that the
previous owner was attempting to re-program the BIOS, then it is no more
likely to be the source of the problem than many, many other failures.

As was suggested before, the most likely failure is the power supply.  Even
though the fan is running, that doesn't mean that all of the outputs are
up to spec.  The fan may run off of the +12V supply and the +5V may have
failed.  It's relatively easy to swap power supplies to test this failure
branch.

The BIOS doesn't do anything itself, it's just a program, so the processor
must be alive enough to run the BIOS if you are going to get anything
out of the system.  The processor doesn't need RAM to start running.  But,
it does need a good clock, and the address decoding to the BIOS ROM must
be intact, and the data bus must be working..  Does the BIOS hang off of
the northbridge chip now-a-days?  If so, then that chip must also be good.
And of course, the processor itself must be functional.

With prices being as low as they are, if resetting the CMOS (by pulling the
battery for 30 seconds or so), pulling all cards out, and swapping power
supplies doesn't show any sign of life, then it probably isn't worth any
more effort to get it going.

marcus hall
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