Apple may have managed to massage a G5 processor into the new iMac, but that doesn’t mean the company is ready to unveil a PowerBook with the same chip. Apple said it was able to cool the G5 in the new iMac, which is only two inches thick, with an air intake hole near the speakers at the bottom of the machine and by the use of three fans — one near the hard drive, one near the chip and another as by the power supply. Some consider this feat a step toward a G5 PowerBook, but Greg Joswiak, Apple’s vice president of product marketing, cautions that it would be tougher to build the current chip into a notebook. “The challenges of cooling a G5 in a PowerBook design are significantly greater,” he said, noting that a PowerBook has far less room for cooling tricks.