ASUS X99-PRO Motherboard

Slots

Socket LGA2011-v3 processors have a maximum of 40 PCI Express 3.0 lanes (some models have only 28 lanes) for video cards. This allows a very high-end configuration for the PCI Express x16 slots when a CPU with 40 lanes is installed, but the exact configuration used will depend on the model of the CPU that will be installed.

The ASUS X99-PRO comes with three PCI Express 3.0 x16 slots (PCIEX16_1, PCIEX16_3, and PCIEX16_4). With a 40-lane processor installed, the board supports x16/x16/x8 configuration. With a 28-lane CPU, the board supports x16/x8/x4 configuration. In both cases, the last slot (PCIEX16_4) shares bandwidh with the on-board M.2 slot; if this M.2 slot is used, this PCI Express 3.0 x16 slot is disabled.

There is also one PCI Express 2.0 x16 slot (PCIEX16_2), which works at x4 speed (x1 speed if the additional USB 3.0 ports are enabled), and two PCI Express 2.0 x1 slots.

The motherboard supports three-way SLI and CrossFireX setups, with up to four GPUs.

When installing dual-slot video cards, you “kill” the slot immediately to the left (looking at the motherboard with its rear connectors facing up) of the slot being used. Therefore, if you install a dual-slot video card in the first, second, or third PCI Express x16 slot, you will be unable to use the slot to its immediate left. You can only install a dual-slot video card at the fourth PCI Express x16 slot if you are using a case with eight expansion slots.

Figure 3: slots

THe X99-PRO comes with two M.2 slots. One of them is shown in Figure 2. However, this slot supports only PCI Express M.2 cards, thus not compatible with SATA M.2 modules. This slot shares bandwidth with the fourth PCI Express x16 slot (PCIEX16_4). The other M.2 slot is available as a PCI Express x4 add-on card, also not supporting SATA devices.

Figure 4: M.2 slot