GPU PCIE x16 question GA-Z77X-D3H LGA 1155 Z77

[igyb]

I just bought this board and am about to hook it up. It has 3 Pci-e x16 slots. Does it matter which I use for my GTX Titan? I only have the one card. I am hoping I can put it on a lower slot so I have more room for my hard drives but have heard its recommended to put it in the highest slot and that using another slot could slow down the speed to x8 instead of x16. Is this the case with this board?

[TFisher]

Yes.
This is from the spec sheet for your board.

Expansion Slots 1.1 x PCI Express x16 slot, running at x16 (PCIEX16)
 * For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.

2.1 x PCI Express x16 slot, running at x8 (PCIEX8)
 * The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.
 (The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
 * PCIE Gen.3 is dependent on CPU and expansion card compatibility.

3.1 x PCI Express x16 slot, running at x4 (PCIEX4)
 * The PCIEX4 slot shares bandwidth with the PCIEX1_1/2/3 slots. The PCIEX1_1/2/3 slots slots will become unavailable when a PCIe x4 expansion card is installed.