http://blog.wired.com/business/2007/...control-a.html
While it's a relatively easy matter to disable one core, Intel wouldn't be able to effectively produce a tri-core processor at this point because of the way the company currently approaches quad-core -- slapping two dual-core dies into a single-socket CPU. AMD, on the other hand, can do tri-core due to its Direct Connect architecture, which provides a dedicated channel between the CPU cores and from each CPU out to the system memory.

http://www.xbitlabs.com/news/cpu/dis...914212726.html