I'm having some problems with my G5 at the moment and would appreciate some advice. My G5 is a dual 2.5 GHz PPC running 10.4.11. Yesterday the Mac kept freezing and sending the fans mad and as I have 2 Hard Drives installed, I booted up from the second drive to try a Disk Utility repair on the first drive. Disk Utility reported that HD1 was OK, but trying to restart the Mac in HD1 got me as far as the grey loading screen and then the fans sped up and that loading wheel just kept going round and round.

OK, I thought, at least I can work from HD2 and that was fine for the rest of the day. This afternoon however the same has happened with HD2; restarting gets me to the grey screen with the spinning wheel and then there's an ominous circle with a diagonal line through it where the grey Apple logo should be, like a No Left Turn sign without the road bit.

At the moment I can't locate my Install Disks but is there anything else I could try?

The last time this happened to me on a G5 it was due to faulty memory. Can you try booting with just one stick in at a time?

Will give it a try, thanks.

Check fans and vents for dust as well. My G5 iMac started playing up - I found one of the vents was plugged up with fluff. I removed it and after that it’s been running well.

Does it start up if you do a safe boot (restart with the shift key held down for up to a minute or so). It takes longer than a normal start up, as it does various hardware checks and disables non-essential system extensions (.kext files).

If that works, try a normal restart again.

Hi there. Thought I'd update with an odd occurrence. I managed a normal start up in HD2 and that has been going along OK, no freezes, etc. I thought this afternoon I'd try restarting into HD1 and see what happened and then proceed with using the advice as detailed above. I was surprised that the restart went OK (if a little slow) and the G5 has been happily working away for over three hours now.

Because the fans seemed to be starting up a little more than normal I opened up Activity Monitor to have a look at CPU Activity only to find that someone appears to have stolen one of my CPU's! Where there should be two, I now have only one! System Profiler confirms this:

Machine Name: Power Mac G5
Machine Model: PowerMac7,3
CPU Type: PowerPC G5 (3.0)
Number Of CPUs: 1
CPU Speed: 2.5 GHz
L2 Cache (per CPU): 512 KB
Memory: 3.5 GB
Bus Speed: 1.25 GHz
Boot ROM Version: 5.1.8f7

While I'm happy that the G5 is working again I'm wondering what to do next. Has anyone any idea what could cause this? How worried should I be about the remaining CPU and am I OK to keep using the G5 or should I take it in for repair? Thanks in advance for any comments.

Have you got the original system install discs - if so, try booting into the Hardware Tests (see instructions on the disc), which will test all major components, including the processor(s).

You could try taking the side off, the plastic CPU cover things and reseating the CPUs. That usually works.

Interesting. I wonder if you could install the CHUD tools from Apple - it'll install a control panel called Processors - you can set up some different things with it. I doubt if it is a software issue, but I wonder if using the CHUD tools might help confirm whether it's a hardware CPU shutdown or something in software.