Seems fixed. I re-installed CentOS 7.2 three more times. It hung during the first installation attempts, and refused to reboot after the 2nd attempt. On the final install the OS seems stable.  I have not encountered a kernel panic that prevents booting. I left HPC disabled in BIOS. I am wondering how reliable it is to install the OS via a USB stick.
I'm having difficulty getting Linux to work with an R815 that has Opteron 6200 series chips installed.  Would like AES and 16 cores per CPU. Opteron 6100 series chips work fine. I tried Opteron 6272 and Opteron 6274 chips. During startup get a kernel panic, NMI (Non-Maskable Interrupt) errors, or CPU #27 errors. I tried the following OSes: Ubuntu Server 14 Ubuntu Server 16 Ubuntu Desktop 16 CentOS Server 7.2 (Seemed promising until I rebooted.)  On each of these I tried repairing the OS after the reboot failed, but I can't even get back to a command prompt. I've tried various BIOS options, but nothing seems to be a permanent solution. 
Opteron 6200 Series + R815 + Linux = Kernel Panic