This is definately a marketing move, this will sure help regain market share. But it's also a technical move, due to the fact if I bought a Xeon5100 server, When this system starts to bog down, I can go from 4 cores to 8 cores relatively painlessly.
This is also only a stop gap solution, as Intel is coming out with a true QC later in '07. They are already working on a replacement technology for the current FSB, like AMD's approach - CSI (I believed it was named)
Intel is working on multiple fronts simultaneously - 2xDC; QC; multiple FSBs on server mobos; 45n; Geneseo, CSI, etc
Although I'm a self-pronounced Intel fan boy, I can clearly see the technical superiority of AMD's approach. Intel also is following AMD's lead, as well as the other way around.