AMD platforms.
For the Intel platform (more exactly for the 45 nm Penryn processors), NVIDIA prepares the C73 chipset, while the C72 chipset is reserved for AMD’s socket AM2+ Phenom processors. The most important difference between them is the higher frontside bus support and the memory type used. While C72 supports 1333 MHz frontside bus and DDR2 memory running at a frequency of 800MHz or 1066MHz, the C73 chipset will use the faster 1600MHz frontside bus and the much newer, just released in fact, DDR3 memory running at 1600MHz. Both of these chipsets will be shipped in two distinct versions, denoted by the "XE" and "P" suffices. An XE suffix will indicate support for three PCI Express graphics slots with a full 16 lanes of bandwidth each (3 x16 SLI) pricing at US$150, while a P suffix will support dual graphics slots with eight lanes per slot (2 x8 SLI) priced at US$100-120.
"Only MCP72 series can support Hybrid SLI. C72 early samples will be available to customers by the end of July where mass production slated for October. MCP72 early samples will be available by August with MP targeted for November. C73 will arrive later where early samples targeted for November and mass production in December." Also, the same site reported another AMD centered chipset from NVIDIA, called MCP78, that will be the first GeForce 8 DX10 UMA chipset that supports the new Hybrid SLI technology, HyperTransport 3.0 and PCI Express 2.0 and it will come in three variants: MCP78 U, MCP78 S and MCP78 D. All the variants support the 1x16 PCIe 2.0 standard.
Source: VR-Zone : Technology Beats - NVIDIA Next Gen. PCIe 2.0 GPU & MCP In Nov