On the P55 chipset boards, the NF200 chip allowed full 16x SLI for both video cards. This same technology was used on many boards even before P55. With a PCH there is no IOH/Northbridge so SLI has to be integrated separately, just like on P55 platform. The NVIDIA NF200 chip supports 32 PCI-E 2.5GT/s lanes.
Here is how it works, NF200 takes the native 8 lane 5GT/s bus and doubles the bandwidth to 16x5GT/s so you would have 32 lanes of 2.5GT/S PCI-E bus for 16x SLI. Do not be fooled it doesn’t add PCI-E lanes; instead it splits the ones already present and adds bandwidth. It is really great at consolidating and making sure the proper devices are fed full bandwidth. Although we have 32 lanes of PCI-E bandwidth GIGABYTE says the board only supports 3-way SLI. This is most likely because 4-way SLI would be 8x each card and performance would take a hit. This board also supports CrossFireX which is the ATI/AMD equivalent for SLI technology.
On this board ALL the PCI-E lanes from the processor are fed directly into the NF200. On many X58 boards and P55 boards, only a portion of the PCI-E lanes are fed to the NF200, the reason is that USB3 and SATA6G work off the high speed PCI-E bus, but this board is one of the few exceptions. The new P67 PCH connects to all of these devices through a secondary PCI-E bus, that has its own clock generator, and its own set of 8 PCI-E switches. The PCH then communicates to the CPU through a high speed 20GB/s DMI interface. The NF200 connects to the 4 PCI-E slots through 2 switches.
Many people have mixed views of the benefits of 16x/16x vs 16x/8x SLI, regardless the NF200 is needed for proper SLI on LGA 1155 motherboard. This motherboard will probably perform exceptionally at SLI with the NF200 because all the PCI-E lanes from the processor are used solely for the PCI-E slots.
This board has two PCI-E clock generators, both are the same model: ISC9DB403DGLF. These clock gens’ spec says they put out a clock between 50-100 MHz. They are used specifically for PCI-E. I will cover the purpose of the second clock generator a little later in the PCH section. Along with clock generators the board has two PCI-E switches for SLI; if a 3rd card is inserted then one video card goes down from 16x to 8x. This board utilizes two ASMT PCI-E switches to switch a native NF200 16x,16x configurations to 8x on each PCI-E port for SLI.
if i plug my X-FI PCI-e sound card into one of the remaining PCI-e slots will the other PCI-e slot drop to x8?
