Two GPU Configuration on a GA-Z77-D3H

[cassini_huygens]

Hi everyone.

I'm looking to install a second GPU dedicated to mining on my motherboard, and had a question about how I would go about configuring the PCIe lanes. Currently I have one RX-470 running in the PCIe3.0x16 slot, and I plan to install the second GPU in the PCIe2.0x4 (physically 16 lanes) below. As far as I know, GPU mining cards are not bottlenecked by PCIe bandwidth, but there's no sense in restricting it to 1 lane if I wouldn't be using the remaining 7.

Relevant system specs:
CPU: i7-2700k (has a maximum of 16 PCIe lanes, taken from intel's ark site)
MB: GA-Z77-D3H (1.1)

I am aware that with my board the primary GPU would be cut down to a x8 configuration, and that I would not be able to use the x1 slots when the second physical x16 is enabled in x4. What options would I have to enable in the board's BIOS to indicate that I'll be running a x8/x4/x4 configuration with 4 of those lanes not being used?

Note: I tried to go into the BIOS and enable the PCIe x4 slot in the PCIE Slot Configuration setting (changed it from Auto to x4) with nothing in it, just wanted to see if the primary GPU was cut down to 8 lanes on the spot, and the computer crashed and reset some of the BIOS settings because it could not boot correctly. I went ahead and reconfigured the BIOS and booted into Windows just fine (checked CPU-Z to see that the GPU was still getting all 16 lanes). I'm not sure why that happened.

 

[k1114]

The 3.0 x16 slot is the cpu's lanes. The mobo has 8 more lanes of pcie 2.0 which go to the x4, x1, pci slots, lan and usb. Page 8 in your manual shows a block diagram.

So with 2 gpus, the rx 470 will run at 3.0 x16. The second gpu runs as 2.0 x4 with extra lanes used for the other devices and disabling x1 slots 2 and 3.

There is nothing you need to do in bios.