
From Newegg.com
With only 20 Amperes per rail we de-rate that to 10A or 120Watts to see if the machine will last years.
The 970 TDP from https://www.techpowerup.com/gpudb/2620/geforce-gtx-970 is 148 Watts.
While this machine MIGHT work I fear over time will experience troubles. Even if we assume the full 20A this is over 50% of that rail and not a good place to start a new PC.
Next time, stick to a single rail. The Wattage was fine, just those rails hurt.
In closing it could be something else but the PSU broke one of my design rules.

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