Dan O is correct,
The FSB (front Side Bus) which ran at 400Mhz or 533mhz between the processors & the North Bridge chip which connected to a memory controller and a south bridge chip to PCI slots, Network controllers and HDD controllers.
In 2008 the QPI bus replaced the FSB and opened a new leap forward in processor speed
QPI buses run speeds up to 8 Gigatransfers per second. The features of a North Bridge are all inside the CPU as well,
Not enough yet?
The old Xeon's in your board have 604 pins that plug into the board,
The E5-1607 (which is not a dual CPU processor) has 2011 "pins" on the mother board that connect to pads on the CPU. (reversed)
Intel has a Tock \ Tic strategie so that customer can upgrade a board's CPU. This means when they design a board for a new CPU, (the tock), about 1 year later the Tic CPU releases and is usually a drop in replacement as far as the hardware is concerned. In the current CPU's the E5-1607 would be the Tock and the E5-1607v2 is the Tic. The computer technology leaps ahead so fast that the CPU's that come after the E5-1607v2 are going to need new mother boards to support the newer features.