IBM i 7.5 is not supported on IBM POWER8 systems

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IBM® POWER8® systems will not support IBM i 7.5:
  • IBM POWER8 8286-42A, 8286-41A, 9119-MME, 9119-MHE, 8284-22A, 9080-MME, 9080-MHE, 8284-21A