HPE BL660c Gen8 reboots with no kdump or errors, UMCE events are logged in BIOS

Issue

• HPE systems BL660c Gen8 system reboots apparently randomly or during a ramp-down (idling after heavy usage)
• No traces are left in logs, remote syslog or even monitoring the remote serial interface
• Server does not hang; it necessarily reboots
• HP ASR watchdog is disabled

• Remote serial port shows a similar output:

  =~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2016.09.02 02:42:56 =~=~=~=~=~=~=~=~=~=~=~=
  login as: Administrator
  Administrator@192.168.0.1's password: 
  User:Administrator logged-in to ILOXXXXXXXXXX.(192.168.0.1 / 8BAD::F00D:DEAD:BEEF:C0DE)
  
  iLO Standard Blade Edition 2.40 at  Dec 02 2015
  Server Name: server01.example.com
  Server Power: On
  
  </>hpiLO-> vsp
  Virtual Serial Port Active: COM1
  
  Starting virtual serial port.
  Press 'ESC (' to return to the CLI Session.
  
  Red Hat Enterprise Linux
  Kernel 3.10.0-327.10.1.el7.x86_64 on an x86_64
  
  server01.example.com login:<ESC>[5n<ESC>[7l<ESC>[0m<ESC>[2J<ESC>[01;01H<ESC>[7l<ESC>[0m<ESC>[2J<ESC>[01;01H<ESC>[7l<ESC>[0m<ESC>[2J<ESC>[01;01H<ESC>[01;01H                                                                                <ESC>[02;01H                                                                                <ESC>[03;01H                                                                                <ESC>[04;01H                                                                                <ESC>[05;01H                                                                                <ESC>[03;01HProLiant System BIOS - I32 (12/01/2015)
  Copyright 1982, 2015 Hewlett-Packard Development Company, L.P. 
  <ESC>[01;01H<ESC>[06;01H
  <ESC>[01;29H1024 GB Installed<ESC>[07;01H
  4 Processor(s) detected, 40 total cores enabled, Hyperthreading is enabled
  Proc 1:  Intel(R) Xeon(R) CPU E5-4650 v2 @ 2.40GHz     
  Proc 2:  Intel(R) Xeon(R) CPU E5-4650 v2 @ 2.40GHz     
  Proc 3:  Intel(R) Xeon(R) CPU E5-4650 v2 @ 2.40GHz     
  Proc 4:  Intel(R) Xeon(R) CPU E5-4650 v2 @ 2.40GHz     
  QPI Speed: 8.0 GT/s
  HP Power Profile Mode: Maximum Performance
  Power Regulator Mode: Static High Performance
  

• A similar UMCE (Unexpected Machine Check Exception) is found in iLO logs:

  Uncorrectable Machine Check Exception (Board 0, Processor 1, APIC ID 0x00000000, Bank 0x00000004, Status 0xB2000000'77000402, Address 0x00000000'00000000, Misc 0x00000000'00000000)