FastSilicon posted a review on Cable-Less Crossfire cards

Though the P965 is the more "value oriented" chipset in Intel's lineup relative to the P975, it has become an enthusiast favorite due to the drastically higher front side bus clocks you can obtain with it on many enthusiast boards. The PCI lane arrangement of the two chipsets is significantly different, with the 975 supporting twin slots with 8 PCI-E lane's directly within the MCH, while the P965 chipset support 16 PCI-E lanes on the MCH, and 4 PCI-E lanes on the ICH using the much lower bandwidth of the Direct Media Interface (DMI) for communications.

Cable-Less Crossfire - P965 and the X1600XT