The ASRock Z87 Extreme4 comes with three PCI Express 3.0 x16 slots, two PCI Express 2.0 x1 slots, and two standard PCI slots.
The three PCI Express 3.0 x16 slots are controlled by the CPU, with the first slot working at x16 when only one video card is installed, the first two working at x8 when two video cards are installed, and with the first working at x8 and the other two working at x4 when three video cards are installed.
This configuration is somewhat different from what we’ve seen in competing products, where the third PCI Express x16 slot is 2.0, is controlled by the chipset, and works at x1, x2, or x4 speed.
All three PCI Express x16 slots support the CrossFireX technology. SLI is supported only on the first two slots.
If you plan to install a dual-slot video card in the third PCI Express 3.0 x16 slot, you will have to buy a case with at least eight slots. (Computer cases usually have seven.)
Since the Intel Z87 chipset doesn’t support standard PCI slots, the motherboard uses an ASMedia ASM1083 bridge chip to connect the standard PCI slot to a PCI Express x1 lane.