The Intel DZ77GA-70K comes with two PCI Express 3.0/2.0 x16 slots, one PCI Express 2.0 x4 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.
This motherboard has one PCI Express 2.0 x4 slot. This slot allows the installation of a PCI Express x16 video card in it, so this motherboard supports three video cards. If you install a video card in this slot, you will need a computer case with at least eight expansion slots. (Computer cases usually have seven.) Usually, manufacturers prefer to install a PCI Express x16 slot working at x4 instead of using a physical x4 slot. Using a physical x16 slot allows users to easily understand that they can install a third video card in it, even if it is running at a lower speed (x4). On the other hand, by using a physical x4 slot, the speed is obvious (x4) and the manufacturer frees up some space on the motherboard to install more electronic components. However, users may not know that you can install an x16 video card in an x4 slot.
The PCI Express x16 and x4 slots support both SLI and CrossFireX technologies.
In order to properly accommodate the additional PCI Express devices that are on this motherboard (PCI Express x4 slot, additional Gigabit Ethernet port, two extra SATA-600 ports, etc.), the board makes use of a PLX PEX8606 switch chip. This chip automatically switches the available PCI Express lanes to the devices that need them. On motherboards with too many PCI Express devices, without a switch chip you need to manually disable devices on the motherboard setup in order to achieve full performance on devices connected to the USB 3.0, SATA-600, and Gigabit Ethernet ports when transferring files at the same time.