Mac Forum / General / General / May 2008

That'll have suffered a serius crash then. Sounds like a sleep issue.
The noise is actually *all* (7 in a single G5, 9 in a dual) of the fans
running at full speed as the OS has crashed, and unable to control them.
It's a safety measure.

Mac OS, for me, has often suffered with issues with sleeping. Sometimes
it is just down to the exact configuration you have, others can be
incompatible, or faulty, peripherals.

The most common things will be USB gadgets or hubs. I had a PCI USB card
that causes everything the have sleep problems, G4s G5s and even PCs.
Check any third party PCI cards if you have any.

You could try checking the crash logs in Console, they may give a clue,
look for any marked 'panic'.

I'd start by running a few maintenance jobs first. Get a copy of
Applejack:

https://sourceforge.net/project/showfiles.php?group_id=79562

And run all the routines as it recommends. This will check the disk for
errors, repair permissions, check for bad prefs files, and clear caches.
You just install it, reboot and hold down command-S as it starts. When
you see the Unixy screen, type Applejack AUTO, and go and get a cuppa.
The fans will run up while this is working, as the OS isn't running.

Next start with the easy stuff, unplugging USB peripherals, try
unplugging all of them first, then reconnecting one at a time. Hubs can
often be the first to cause problems.

Have you upgraded anything, such as a graphics card? I put a flashed
GeForce6200 into mine and that caused a failure to wake after sleep (I
now have a Radeon 9800Pro and that works fine). Third party memory is
worth checking too, Mac OS is very fussy about RAM specifications, and
you could also have a module start to fail.

It can be a long process to fix, and you'll often not know what did it.

One possible cause is bad memory.  I once had a PowerMac G5 that crashed
repeatedly with exactly the same symptoms that you describe.  No hardware
or memory tests were able to pinpoint the cause, and an Apple-certified
technician ran it for days in his shop without managing to diagnose the
problem.

I later bought some extra memory and did some swapping until I found that
the crashes were always associated with one particular DIMM, and they
ended when that DIMM was removed.  The technician confirmed my diagnosis
and got the memory replaced under warranty.  The bad DIMM was from Apple,
but the extra memory I bought was third-party and worked fine.

archtops <joev@archtop.com> schrieb:

This might be a bad or unconnected thermal sensor.
CPU-Calibration might be gone.

Florian

Pleased to report symptoms abated. Suspect USB wierdness. Many thanks
to all for sage and generous advice. Applejack is good!

Best,

-jv