As seen in previous nVidia nForce chipsets, the new nForce 4 is a single chip solution. This means that instead of dividing the chipset into a Northbridge (for video and memory input which communicates directly with the processor) and Southbridge (peripheral and drive input, communicates with Northbridge), all functions have been placed on a single integrated core logic circuit.

This design innovation helps to reduce data bottlenecks by eliminating the data bus between the Northbridge and Southbridge chipsets completely. Given the unique architecture of the Athlon 64 processor, in which the memory controller is on the CPU itself rather than the chipset, this kind of one-chip solution makes a lot of sense.

nVidia's nForce 4 platform is currently available in three distinct variants, with a fourth version apparently following in the near future.

The three main variants available now are:
nVidia nForce 4 - a socket 754 solution which supports both Athlon 64 and Sempron processors
nVidia nForce 4 Ultra - a solution for Athlon 64 and FX processors in the socket 939 formfactor
nVidia nForce 4 SLI (Scalable Link Interface) - a solution for socket 939 Athlon 64 and FX processors, featuring dual PCI-Express slots for dual SLI operation with compatible video cards.

As you might expect, there are abundant similarities between each of these nForce 4 chipsets. Each of the three versions currently released handles different situations, but each also offers a similar feature set to the user, the biggest of which is PCI Express.

PCI-Express support

The most awaited feature of the new nVidia nForce 4 chipset is PCI Express, and it is arguably the most significant. For some background on PCI Express and how it works, see our article on the technology here. Each of the three nForce 4 chipset variants includes a full 20 PCI Express lanes, 16 of which are reserved for the PCI Express graphics slot. The other four are split into 4 PCI-Express x1 lanes for peripheral slots. This enables Athlon 64 users to take advantage of the newest PCI Express video cards and other components.