Console: diagnosing intermittent crashes?

[doobydoooby]

I have an aging mac pro 2008 3,1 that I'm just hoping is going to keep running until whatever new Mac Pro eventually comes gasping over the hill...

But it keeps crashing and there doesn't seem to be much of a pattern. It always happens within a minute or two of first powering up and logging on to the machine, and it always completely turns off and reboots without any warning. Most of the time when the mac reboots it does not give me a system report for some inexplicable crash, it just starts up as normal (sometimes one chime, a bit of fixing, second chime and start, other times just one chime and off we go as normal). Occasionally when it reboots the fans go into overdrive sounding like a jet engine and I need to reboot via the OS to calm it down.

Occasionally my mouse doesn't work at all on reboot which maybe hints it could be a USB driver causing the issue. I've tried the mouse in many different USB ports and none seem to be better or worse than others (including a USB 3 PCI slot) so seems unlikely to be a USB motherboard issue. It frequently happens when I'm using a web browser but that could be firefox or chrome so that may not be relevant.

So I'm left with a slightly poorly mac which randomly reboots and no system report being produced. And since it isnt easy reproduce, removing peripherals hasnt really helped me to isolate whats going wrong. Would anyone have a guide as to where I might find a hint what the problem is using console? I would say this happens about once every four or five times I reboot, so its kinda random but far too repetitive to be really random.

Oh and to be clear when it doesn't have a random reboot in those first couple of minutes, everything works perfectly for hours and hours until I turn it off.

Its a Mac Pro 3,1 running 10.13.2 via dosdude's High Sierra enabler. 2 x 2.8 xeons, 16gb ram, SSD startup disk, Nvidia GTX 680 flashed with EFI Rom, USB 3 PCI installed and wifi/bluetooth card installed. Continuity working

Any illuminating ideas where to look in console would be very gratefully received!

 

[ActionableMango]

I'd monitor temperatures to see if CPU, Northbridge, or something else are getting out of hand. That could cause instant shutdown from thermal protection. Your high fans speeds are also a possible indicator of overheating.

I'd check the system log too, but it sounds like you are insta-crashing so there might not be anything there.

 

[doobydoooby]

I'd monitor temperatures to see if CPU, Northbridge, or something else are getting out of hand. That could cause instant shutdown from thermal protection. Your high fans speeds are also a possible indicator of overheating.

I'd check the system log too, but it sounds like you are insta-crashing so there might not be anything there.

Indeed normally there isnt a system log being generated, I can only see the last items running until the crash.

Temperatures seem to be fine - the two CPUs are running at 36 degrees c and all the other istat temperatures look okay below 50 degrees. Only the ram is running hotter at 70 degrees c but I gather the Mac pro ram always runs hot.

 

[ActionableMango]

If you have a spare drive, I'd do a clean install and see if you have a problem there.

I suspect a hardware problem, but doing this would confirm.

You could also try Apple Hardware Test, but I don't have much faith in it.

After all that, it's a matter of reducing hardware to minimum configuration in order to troubleshoot for the problem part as a process of elimination, and hopefully it's a cheap option causing the problem and not, say, the logic board.

 

[lowendlinux]

Indeed normally there isnt a system log being generated, I can only see the last items running until the crash.

Temperatures seem to be fine - the two CPUs are running at 36 degrees c and all the other istat temperatures look okay below 50 degrees. Only the ram is running hotter at 70 degrees c but I gather the Mac pro ram always runs hot.

Actually there's a log of everything going back weeks