Mac Pro 3,1 with flashed 6870. Power supply or video card problem?

[ratfink]

I have a 2008 Mac Pro 3,1 that was bought new and has given me absolutely no issues until recently. I flashed a 6870 and everything was going great for several days. Then we had a power failure. The system was on a Tripp-Lite UPS (I had no idea about the sine wave power supply). I wasn't home, so the power supply eventually gave out and the system lost power.

Now, the UPS itself is dead. It won't power on, it just lights up for 1 second and shuts off. The Mac will run fine for anywhere from 30 minutes to 24 hours before powering itself off and rebooting. Sometimes it gets stuck in a loop of reboots and sometimes it comes right back up. The issue never happened with high loads on the GPU such as Steam games on max settings. It usually happened with youtube videos in Chrome, oddly enough.

I've swapped out the 6870 and put the old 2600 back in and now have no issues. So my question for those in the know is, did I kill the power supply or could it be something else? The 6870 uses two power cables and the 2600 just uses the bus.

 

[ActionableMango]

The Mac will run fine for anywhere from 30 minutes to 24 hours before powering itself off and rebooting. Sometimes it gets stuck in a loop of reboots and sometimes it comes right back up. The issue never happened with high loads on the GPU such as Steam games on max settings. It usually happened with youtube videos in Chrome, oddly enough.

These problems occur on your MP while plugged into the dead UPS, or directly to the mains power?

 

[ratfink]

These problems occur on your MP while plugged into the dead UPS, or directly to the mains power?

They happen without the UPS. The UPS is completely dead now.

 

[ActionableMango]

I am definitely not in the know. But nobody else is saying anything so I might as well take a stab at it.

My wild guess is that the power supply was damaged during the brownout experience provided by the failed UPS which, even when it was working, provided the wrong type of power anyway. Along this theory, the extra strain of the 6870 is too much for the damaged power supply and the 2600 is not.

What I would do at this point is additional process of elimination for further troubleshooting.

First I'd stick the 6870 in a PC and see how it works. This will eliminate or identify the graphics card as the problem.

Second, I'd put a spare drive in with a freshly installed OS on it. If it works, this eliminates either corrupted software or the normal hard drive itself as the problem.

Hopefully nothing expensive is damaged. Good luck!

 

[ratfink]

I am definitely not in the know. But nobody else is saying anything so I might as well take a stab at it.

My wild guess is that the power supply was damaged during the brownout experience provided by the failed UPS which, even when it was working, provided the wrong type of power anyway. Along this theory, the extra strain of the 6870 is too much for the damaged power supply and the 2600 is not.

What I would do at this point is additional process of elimination for further troubleshooting.

First I'd stick the 6870 in a PC and see how it works. This will eliminate or identify the graphics card as the problem.

Second, I'd put a spare drive in with a freshly installed OS on it. If it works, this eliminates either corrupted software or the normal hard drive itself as the problem.

Hopefully nothing expensive is damaged. Good luck!

Thanks for the reply. That was my original assumption as well. The only other option being that the power supply was no longer up-to-par before the 6870 was installed and the power outage was just a coincidence. Either way the power supply would be the problem.

I don't have a PC to test the 6870 in or I would do that. Now I have to decide if I'll just wait for the new Mac Pros and upgrade or if I want to replace the power supply.

Does anyone know if Apple stores have the hardware to test the power supply or if they'd just ship it back to the mothership?