Asus gives the P7P55D Evo a fairly diverse slot configuration, including three PCI Express x16 slots, two PCI Express x1 slots, and a pair of PCI slots.
The way it all works is fairly simple: if you have a single graphics card plugged in to the first slot, you get a full 16 lanes of PCIe 2.0 connectivity from the Core i5's integrated link. With two cards connected, the processor's available lanes are divided between two x8 slots. The third x16 slot is electrically wired to run at x4 speeds and is attached to the P55 PCH (and thus wholly unsuited for a third graphics card, since P55 connects to Core i5 via the comparably-slow DMI). Similarly, the two x1 slots tie into P55, which includes eight available PCIe 2.0 lanes.
When you add up those six PCIe lanes, the PCIe Gigabit controller, and the onboard storage controller, it's no wonder Asus used a PCI controller for its second Ethernet chip.
Uup until now, we haven't heard much about the extent of multi-GPU support on Core i5. ATI's CrossFire is assumed, given Intel's support for the technology historically. However, we can also confirm that SLI will likely be included in the retail version of this board, too. We dropped in a pair of GeForce GTX 280s using Nvidia's 186.18 driver and had no problem enabling Nvidia's multi-card capability. This will very likely differ from vendor to vendor and board to board, depending on licensing. But just as most every X58 motherboard came to include SLI support, we hope P55 will be similar.