The odd thing is that I cloned the SSD that has worked for years as a test, a Samsung 840 Pro 256Gig.
And the clone 1TB 850 EVO booted and works. So I tried twice on the original SSD and nope won't boot except when the W10 install resets back to W7.
The old C drive was the same cloned size on both SSDs.
So looks like I've got a permanent W7 boot SSD now. Small loss, I'll just use the clone.
Oh,... a 3930 6 core cpu from 2012. X79 Asus Sabertooth MB.