I just found out something interesting. My Mac Pro from sig, has AcBel PSU (614-0455). Few days ago I disassembled Mac Pro mid 2012 which has Delta PSU (614-0454). Both PSUs have exactly the same specs. And now why this topic...loudest fan in my Mac iz Power Supply fan. Fan in both machines are running at the same speed, but mine is definitely louder. Is there a chance that fans are not the same for different PSUs combinations ? One more thing, is there a quality or reliability difference between these PSUs, because internally they are not identical ?