Here’s how benchmark results compare the August 2005 iMacs with the June 2004 Power Macs using the same speed CPUs: Unlike top-end Power Macs that have a memory bus running at half of CPU speed, the G5 iMacs ran their memory bus at one-third of CPU speed, making them a bit less efficient. The Mid 2004 iMac G5 came in 17″ and 20″ versions, using the same IBM PowerPC 970fx (G5) CPU that had already been used in the first generation Power Mac G5s (June 2003) as well as the second (April 2004). The iMac G5 has a single CPU – 1.6 and 1.8 GHz on the 17″ model and 1.8 GHz on the 20-incher. Not counting the stand, it was about 2.5″ thick. Where early Macs had been cute little boxes with 9″ screens, the first iMacs were curvaceous enclosures with 15″ displays, and the G4 iMacs had hemispheric bases with 15″ to 20″ screens that seemed to float above them, the iMac G5 put all the electronics directly behind the display. The G5 iMac introduced a new form factor to the all-in-one Mac. The PowerPC G5 came to the iMac in August 2004, over a decade after that. The first Power Macs arrived on March 14, 1994, 10 years after the first Mac – the Power Mac 6100, 7100, and 8100, running the PowerPC 601 CPU at speeds of 60, 66, and 80 MHz respectively. The PowerPC platform had a long life on Macs.
