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G5 DP 7.2 won't boot

I just got this one. Excitedly set it up and turned power on. Aaand it won't boot.
  • power led is lit when button is pressed, it goes off right after
  • fans do rotate slowlishly.
  • fans do rotate at full speed when the plastic cover is removed. Also a red led is lit on the logic board. Both go back to normal when cover is put back
  • no chime
  • no picture
  • There is no pram battery
  • 2 Simms on #1-slots
  • display adapter (radeon 9600) on the agp-bus
  • no other leds are lit on the logic board
  • computer is relatively dust free
  • power goes off when power button is kept pressed ~10 seconds

What have I done:
  • reseated memory and display adapter
  • booted several times with various configurations of no memory installed, with memory, no display adapter installed, with display adapter
  • also tried with and without a hard disk. I do not have a hdd sled.
As I don't have other simms, display adapter nor battery I can't swap parts. Battery is in mail and should arrive next week.

I should add that the very first boots did not succeed at all; the fans twitched and then kept still. I removed the simms (those were on #4-slots) and moved to #1 slots, reattached the display adapter. At some point those actions (or the matter that the computer got fed enough power as it had been without power for a couple of years) helped and I was faced with the symptoms above.

Any help is appreciated. This is a beautiful computer and I would love to get it running.


Well-known member
I have to assume you meant Dual 2.7. A dual 2.7 is liquid cooled, right? If the coolant has leaked at all, it can damage the processor and/or dump liquid into the power supply located in the bottom of the tower. I’d visually verify there are no leaks before troubleshooting any further with this machine.

If the liquid cooling has indeed leaked, it has been known to kill the processor card, the power supply, or even the motherboard in severe cases… often in spectacular fashion!

It’s usually quite obvious if leaking has occurred… rust, crystal deposits, or puddles of liquid at the lower end of the tower. If there’s no signs of any of that, and it’s still showing signs of life, hopefully it’s nothing major. Otherwise, major leaks in such systems are often a total loss.

The plastic cover needs to be installed to ensure proper airflow, it is normal for the fans ramp up to max if it is not in place. RAM sticks needs to be installed in matching pairs with these machines.

I’m not sure if a PRAM battery is required in a G5, might try zapping the PRAM to see if that helps. Otherwise, install a new PRAM battery and see if that changes anything.

I know these systems need to be thermally calibrated whenever work is done to the cooling system or the processors are swapped. Not sure where that is stored… maybe in PRAM?

If it needs to be thermally recalibrated, there is a special disc you need to burn and boot from to do that. Of course, it needs to boot in the first place to do that.

Hopefully, it’s nothing major, but often times a liquid cooled G5 can be a gamble. If you do get it running, a flush and refill of the liquid cooling is strongly recommended. Depends on the pump version yours has, but there are guides out there. Haven’t gotten that far yet on mine, but it looks rather complex and time consuming.
According to serial numbers lookup on everymac.com this is a powermac7,2. Thats where i got the info on the subject. 🙂
This is not liquid cooled, there are ordinary cooling blocks.

I have some more information on this. It seems to boot when it is cold, ie been powered off overnight. I even managed to boot from a G4 dvd until it froze. The image on the display was very distorted, and thus I suspect that the graphich adapter might be at fault. I guess the image should be readable at least when booted from older dvd, right?

New symptom is that after some time powered on, maybe 5 mins, the fans start gradually spin faster and faster until they are full on. Maybe I did not originally keep it powered on long enough to notice this.

Does this computer support boot from USB?
Are there restrictions on what kind of hdd´s can be used?


Well-known member
It sounds like the characteristic behaviour I have observed in machines with a failed processor — or an overheating processor. But I am no tech.

As someone who has gotten a lot of these going, all the same, I’d have said that a sensible first step would be to extract the processors, remove the heatsinks, apply new thermal compound, reassemble and reseat the processors in the same slots each came from (this is important), to see if the problem is purely mechanical, shall we say. If that doesn’t work, you may have a failed processor.

The machine will run with one empty processor slot (not sure if top or bottom matters, mind!), and this is useful in identifying which processor has failed. Note that if you were to obtain a replacement, the machine will need recalibrated using the relevant service utility optical disk.
Update. Finally got a new display adapter and that has solved the distorted picture issue. I have now run this computer three days, most of it of course hibernated or power save mode, what ever it is called.
I have also disabled one cpu in open firmware, and that may have solved the issue of the computer not being able to boot. During tests I removed one cpu physically, and tried running with only one, swapping the cpu between boots. This did not lead to anything however.
I will continue to test with removing one cpu at a time and switching sockets.