The ASUS P8Z77-V PRO comes with two PCI Express 3.0/2.0 x16 slots, one PCI Express 2.0 x16 slot, two PCI Express 2.0 x1 slots and two standard PCI slots.
The two PCI Express 3.0/2.0 x16 slots are controlled by the CPU, with the first slot working at x16 when only one video card is installed, and with both working at x8 when two video cards are installed. Since these slots are controlled by the CPU, they will offer PCI Express 2.0 bandwidth (8 GB/s at x16) when a “Sandy Bridge” CPU is installed, but PCI Express 3.0 bandwidth (16 GB/s at x16) when an “Ivy Bridge” CPU is used.
The third PCI Express x16 slot is 2.0 and always workss at x4 speed. If you want to install a dual-slot video card in this slot, you will need a computer case with at least eight expansion slots. (Computer cases usually have seven.)
ASUS did a great job by using different colors at each PCI Express slot, so you can easily identify their speeds: blue for x16/x8, gray for x8, and black for x4.
The PCI Express x16 slots support both SLI and CrossFireX technologies.
Since the Intel Z77 doesn’t support standard PCI slots, this motherboard uses an ASMedia ASM1083 chip to connect them to PCI Express x1 lanes.