It seems that Steve Jobs got screwed over by IBM, because IBM didn't care that much about making the CPUs that Jobs wanted for Macs, because IBM decided that game consoles were more important. 'IBM Inside' every next-generation game console: Sony Playstation3 (IBM 'Cell' CPU) Microsoft Xbox 360 (IBM 'Waternoose' CPU) Nintendo Revolution (IBM 'Broadway' CPU) which will ensure tens of millions of IBM CPUs sold every year, compared to maybe 5 million Mac CPUs every year. even if it was more than 5 million Mac CPUs, it would still almost certainly be less than 10 million. so it seems that is one of the major reasons why Apple has hooked up with Intel for CPUs
related article http://arstechnica.com/columns/mac/mac-20050607.ars
