Leading up until the Pentium Extreme Edition 840's launch, there was much speculation about whether Intel's dual-core processors would contain one piece of silicon, or two individual piece of silicon ala. Pentium Pro style. That question has been answered. Intel's entire current Pentium D line makes use of a single-silicon core code-named "Smithfield", but the innovation ends there. Smithfield is, quite literally, two Prescott cores glued side-by-side.

The following die photograph shows us just how literal that statement is:

Smithfield is a gigantic die indeed, coming in at 230 million transistors, and taking up 206 sq. mm of space. Fortunately, Smithfield has additional power consumption enhancements. SpeedStep power management, along with C1E, TM2 and EIST technologies, aids in managing the power draw and heat output of the two cores. We already know how hot one Prescott can get -- now imagine two running in unison. Unfortunately, in order to keep heat output at manageable levels, Intel has had to lower the clock speeds of both cores, as we saw earlier.

Since Smithfield is really just two Prescott cores, you can expect the same technical specifications. Each core sports a hefty 1 MB of L2 cache, they both support EM64T (Intel's implementation of AMD64), SSE3, Execute Disable Bit, and it all runs on an 800 MHz front side bus -- and I really do mean all of it. This is where the ugly facet of Intel's implementation rears its even uglier head.

Not only does the 800 MHz shared FSB provide a means of communication to and from the outside world, but this same FSB is used for inter-core communications. Yes, you heard it right: memory accesses, general input/output, and even cache updates all happen over this limited 6.4 GB/s bus. As I briefly talked about in my Athlon 64 X2 4200+ review, 6.4 GB/s is an awfully slow bus as far as cache updates are concerned. L2 cache speeds on the Pentium 4 can approach 13 GB/s, and L1 cache is even faster. Limiting the cache speed like this will not bode well for the Pentium D 820.

Intel's direct competitor, on the other hand, designed their current generation of processors with dual-core in mind. The end result is a very efficient architecture, with on-die inter-core communication, a crossbar, and a system request queue component.

All technicalities aside, we all know that when it comes down to processors, its all about performance. Intel's Pentium 4 may have been less efficient than the Pentium III, but it has more than made up for that in clock speed. I can apply the same logic here: Intel's dual-core implementation may be less impressive than AMD's from a technical point of view, but if the end effect is the same or similar, I can (and will) forgo the nit-picking.