'08 Mac Pro 3,1 restarts on bootup

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'08 Mac Pro 3,1 restarts on bootup

I have a 2008 3,1 Mac Pro and suddenly will no longer boot into OS. It has 2 HD...one with ElCapitan and the other with Snow Leopard but will flicker and reboot halfway through boot screen. Ive tried to boot from both disk and have even removed one HD while the other OS remains. The only difference is the Snow Leopard will boot to a blue screen and hang, but ElCapitan constantly reboots after half way on boot up. Things I've tried so far:

• Safe Mode (still reboots half way through)

• reset PRAM and SMC (still reboots half way through)

• Boot from Snow Leopard DVD (reboots half way before DVD loads)

• Boot from Recovery (still reboots half way through)

I booted using Command-V and snapped a few images on screen if anyone might see whats going on! After whats showing on 3rd image system rebooted.

Posted on Aug 24, 2019 2:16 PM

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Answer 1

Aug 24, 2019 8:26 PM in response to Mark Pilkinton

Ha! My thought exactly on the blue screen. It’s a different shade of blue and maybe the background color of my snow leopard desktop. As far as Start Up Manager...yes. It works just fine and never reboots and the same when in Single User mode. I decided to try a third hard drive and do a install from DVD snow leopard, but reboots and hangs. Here is an image of the Single User screen. And thanks for your response!

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Answer 2

Aug 24, 2019 5:31 PM in response to Mark Pilkinton

The last item on the screen (Bluetooth connection) is not at all deadly.

Previous Shutdown cause: -2

from an article posted by a developer, we have learned that:

shutdown cause 0 is power problems, and

shutdown cause -3 is Multiple temperature sensors exceeded the defined limit.

So I don't think it is too much of a leap to say that Previous Shutdown cause: -2 MAY be involve a temperature sensor.

I think it is odd that your 10.6.8 crashes to a BLUE screen, unless you were running Windows there. MacOS does not have a blue error screen.

One very simple thing your Mac can do is boot to the Startup Manager (hold Option at startup. As I am sure you know, this brute-force discovers what drives are available and which appear to be bootable, and draws an Icon for each.

The question on my mind is, ¿can you sit there running that ROM-based software for as long as you want, or does that power down as well?

What happens when you try to boot in Single-User mode (just gets to the Terminal command-line and stops there, rather than booting up MacOS) ¿can you sit there for a while, or does it shut down?

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Answer 3

Aug 25, 2019 10:02 AM in response to Grant Bennet-Alder

I think I’ve got another card I can test and see. I can’t remember the Snow Leopard desktop color, but I’m getting down to the last few things I can do. I hate to trash the computer, but don’t plan to spend much to fix it.

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Answer 4

Aug 25, 2019 12:34 PM in response to Grant Bennet-Alder

Unfortunately the extra video card I have is for my old G5. One question, does the Start Up Manager by pass the video card? When holding down “option” and looking at the screen with options to select which hard drive or DVD to boot from, everything looks fine with no problem until system try’s and boot from any selected drive.

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Answer 5

Aug 25, 2019 5:55 PM in response to Mark Pilkinton

It uses a graphics method I refer to as "simple" graphics mode. No acceleration, nothing fancy at all, it just writes into a buffer, points the display hardware at that buffer and says 'go' using methods and resolutions any old graphics card can accomplish. It is thought that Safe Mode uses simple graphics, but perhaps more complicated than Startup Manager, and that is why you could not get through Safe Mode Startup.

There is another twist as well. Your Mac does not require a graphics card to operate. Many Server computers have been run that way. The Mac just creates a gratuitous screen buffer in memory instead. If there were a way to enable screen sharing, you could read it from another Mac. If you are a terminal geek, you may be able to get in with ssh and poke around a little. I am not sure what you could discover that way.

If you can boot it up with the card removed and it stays up and does not re-boot, that adds weight to the graphics card as the culprit.

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Answer 6

Aug 25, 2019 8:07 PM in response to Grant Bennet-Alder

Yes, I agree that the graphics card seems to be the issue if what you’re saying is correct about monitoring using memory buffering when in Start Up Manager. So far everything that try’s to boot further than Start Up Manager crashes and I can see quick flashes like system is trying to load the screen, but finally reboots.

I’ve ran some checks from Single User Mode and after running /sbin/fsck -fy, the hard drive checks out fine. The system never reboots in Single User Mode. I can’t find a command line that checks the video card...is this possible? I’ll grab a used card, but it would be nice to find out if mine is definitely the culprit!

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Answer 7

Sep 4, 2019 10:51 AM in response to Grant Bennet-Alder

Thanks for your help Grant. I got ahold of another video card and that was the issue. It’s not the exact same card and I no longer see the boot screen, but after the OS launches, all is good.

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Answer 8

Aug 25, 2019 6:42 AM in response to Mark Pilkinton

If that blue screen is the color of the Snow leopard desktop, your Mac may have a graphics card issue.

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'08 Mac Pro 3,1 restarts on bootup

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