One of the main features of the socket 1156 CPUs is the presence of a PCI Express 2.0 controller integrated in the CPU. This controller supports an x16 connection or two x8 connections. P55A-UD6 seems to have three PCI Express x16 slots, but a careful look reveals that only the first one is really x16. The second slot works at x8 and is good to remember that if you install a video card on it the first slot also works at x8. The third slot is actually a PCI Express x4 slot controlled by the chipset. You can install a regular video card on this slot, but it will work at x4. Besides that, this third slot does not offer support for SLI or CrossFireX arrays. Keep in mind that SLI support on P55 motherboards will depend whether the manufacturer has licensed this technology from NVIDIA and thus not all motherboards based on Intel P55 chipset support SLI.

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Figure 5: Slots.

Gigabyte P55A-UD6 also offers two PCI Express x1 slots and two standard PCI slots.