2.8 GHz system. A related criticism leveled at Power Mac systems from this time, particularly the G4 Mirrored Drive Doors, was the increased fan noise level compared to older systems. The Power Mac G5 and the end of Power (2003–2006) By the time the Power Mac G5 was unveiled at Apple's Worldwide Developers Conference in July 2003, Apple's desktop range had fallen significantly behind competing computers in performance. The G5 closed much of this gap by moving to the PowerPC 970 processor with clock speeds up to 2.0 GHz, and a full 64-bit architecture. It also introduced a significantly revised enclosure design, replacing the use of plastics with anodized aluminum alloy. Reviews were generally positive. InfoWorld described the G5 as "Apple's best work yet", and said it "delivers on the present need for rapid computing, deep multitasking, and responsive user interfaces — as well as the future need for mainstream computers that rapidly process and analyze massive data sets." PC Magazine again awarded the Power Mac G5 with its Award for Technical Excellence for 2003. However, the G5's heavy weight (10 pounds more than the previous year's Quicksilver Power Mac G4), limited internal expansion options, issues with ground loop, and noise in the single-processor models' power supply units resulted in significant criticism of the product. Apple also continued to make unsubstantiated performance claims about the new Power Mac. This resulted in the Advertising Standards Authority for the United Kingdom banning Apple from using the phrase "the world's fastest, most powerful personal computer" to describe the Power Mac G5 after independent tests carried out by the Broadcast Advertising Clearance Centre determined the claim to be false. Another claim made by Steve Jobs at the 2003 Worldwide Developers Conference was that the company would be selling a 3 GHz G5 by mid-2004; this never happened. 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