Lost Circuits took a look at Intel's new Pentium 4 840 EE and 840D processors. Here's a short snip:

In the case of AMD’s Athlon 64 X2, the dual core has one distinct disadvantage, that is, each core has essentially only access to a single channel of memory. A true SMP solution, on the other hand, can utilize both channels for each CPU and, furthermore, take advantage of the cache-coherent Non Uniform Memory Architecture (ccNUMA) which provides memory access through two distinct buses, namely the direct memory interface to the near memory and the HyperTransport to the far “node”, i.e., piggybacking off the second CPU.

In the case of the Pentium4, the question about dual core vs. SMP comes out to as a wash, at least in terms of the memory bandwidth, since even two physically separate processors will share one bus.



Link: Lost Circuits