GPU restart Mac Pro 3rd Gen. Early 2009 with GTX 1070, how to diagnose? Frequent, almost daily GPU restarts. From the console, under System reports, there's a painful record of the Kernel panics. Here's the most recent one:

Thu Sep  7 15:10:19 2017

Event:               GPU Reset
Date/Time:           Thu Sep  7 15:10:19 2017
Application:         WindowServer
Path:                
Tailspin:            /Library/Logs/DiagnosticReports/gpuRestart2017-09-07-151019.tailspin
GPUSubmission Trace ID: 0
OS Version:          Mac OS X Version 10.12.6 (Build 16G29)
Graphics Hardware:   NVIDIA Chip Model
Signature:           8


Report Data:

NVDA(Graphics): Channel exception! Exception type = 0x8 DMA Engine Error (FIFO Error 8)
Channel Info: [0, 0x2, 0x2, 0x9d7]
Version Info: [com.nvidia.web.GeForceWeb, 10.1.8, 0x4e554e, 22510759, 378.05.05.25f01, 1]

Resource Manager Info:
 4443564e 000000d0 a24a219a 697c239f 00000001 00000014 ......etc


Basically, I'm hoping someone can point me in the right direction. Is it hardware related? Software? What else can I provide to help debug?
NVIDIA recommends that the system in which the card is installed should supply 500W: https://www.nvidia.com/en-us/geforce/products/10series/geforce-gtx-1070/

However, Apple warns that across all the PCIe expansion slots, not to pull more than 300W: https://support.apple.com/kb/sp506?locale=en_US

So, my guess is that whenever the GPU power consumption spikes, perhaps when you're playing games or videos, the Logic Board shuts off as a precaution.