AMD has stated last year about tri's,and other combinations being in the design loop. But in reality, it is a common manufacturing problem that is creating a new product. Since AMD is truly manufacturing a quad cpu, a small number of the quad's will have a detective cpu in the quad. Sometimes, it's something simple like running slower than the other cpus, affecting the L3 cache----- so, they disable the single cpu out of the quad. The marketing of the tri's will need some volume of ics, so production of the quad must be running for a while.
Even more interesting in the IC world, Toshiba is in serious talks with Sony about buying the Sony IC production lines. Toshiba is offering over $100B. Sony is quiet about any talks. Toshiba's people are leaking that they want the cell line from Sony included------- which would lower the IBM legal threat over Toshiba's people actions on the design team. Also would help Toshiba slow down the PS3 as a HD player, being a key supplier---MS will be happy. The rumor from Japan is the magic number is 200B, 100B now and the rest on a payment plan. But "official" rumors are sounding boards in Japan, so its a guess, but does Toshiba have that type of cash reserve without help from US friends? Who knows? Who cares?
I wouldn't say AMD's business tactic is anything new.. that's how you've always gotten different CPU speeds from the same type of CPU. They just applied it to their multi-core design. I'd assume that intel can't do this because they're duel duel cores & duel + 1 would slow it down (just assuming. I'm sure it was discussed there vigeriously & that makes sense).