multi core cpus are essentially a single chip with multiple processing cores on it where as a coupled core setup uses 2 or more chips with 1 or more cores on each chip its usually the standard for pcs to use a single multi core chip over multiple chips due to power restraints and bottlenecking "x2 chips = x2 power" however server setups tend to use multiple chips with lots of cores on each for high end and critical applications ie
http://www.ebay.co.uk/itm/Dell-PowerEdge-R810-2-X-INTEL-XEON-6-CORE-E7530-1-86GHz-64GB-RAM-2-X-300GB-HDD-/370580860558?pt=COMP_EN_Servers&hash=item5648572e8e
64GB of ram and 2x 6 Core processors
if your thinking of building a dual processor setup, dont! unless you have a nearly endless supply of money i looked into it not too long ago and the motherboards are very few and far between for home use and there's an endless list of other parts you need on top
Another issue is that coupled processors need a handshake to note whem shared memory is updated, in order to invalidate or update internal caches. There's also a need for a handshake for shared I/O busses. This feature is disabled or doesn't exist on standard PC desktop processors. AMD Opteron or Intel Xeon processors are examples of coupled processors that run on multi-processor chip server motherboards.
Ignoring power consumption, would 2 coupled single core processors or 1 dual core processor be able to plow through the same data in the same amount of time? Assuming clock speeds were even across the board?