Three generations of Power Mac G5 were released before it was discontinued during the Mac transition to Intel processors. The announcement of the transition came in mid-2005, but the third generation of G5 systems was introduced towards the end of 2005. Most notably in this generation was the introduction of a Quad-core 2.5 GHz system. Not only was this the first Apple computer with four processing cores, it was the first to incorporate PCI Express instead of PCI-X for internal expansion. It also required an IEC 60320 C19 power connector that was more common on rackmounted server hardware, instead of the industry-standard C13 connector used with personal computers.