Intel and AMD weren't the first to ship dual-core processors.Read more over here.
The widespread assumption is that the dual-core duel has been fought solely on the PC front, with AMD and Intel vying for the title of first to market. That's incorrect. In fact, IBM beat both companies to the multicore punch, albeit with a non-X86, server processor. That occurred when Big Blue rolled out its dual-core Power 4 chip in 2001, for use in IBM's RISC servers, in 2001.
AMD and Intel announced their respective dual core plans in 2004 and began their first dual-core shipments in 2005. (Here for AMD, and here for Intel.)
Things you may not know about dual-core processors

TechWeb posted five interesting things about dual-core processors, here's the first one: