Help me clear something up re: Asus X99-A II and PCIe slots

Aug 7, 2018
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Hey all,

I have a system here that involves an i7 6850k in an X99-A II mobo. I also have a GTX1080, an Asus PCE-AC88 WiFi card, and an RME AIO DA card for audio. (I do audio/video production...)

I had assumed that the best place for the 1080 was slot 1, as it's the metal reinforced slot, but looking at the mobo specs, I'm beginning to think I may be robbing it of bandwidth.

The manual says:

3 x PCI Express 3.0/2.0 x16 slots* (single at x16, dual at x16/x16, triple at x8/x16/x8)
1 x PCI Express 2.0 x16 slot** (PCIe x16_2, max. at x4 mode, compatible with PCIe x1 and x4 devices)
2 x PCI Express 2.0 x1 slots** (compatible with PCIe x1 devices)

and also:

*PCIe x16_1 and PCIe x16_4 slots share the same bandwidth. PCIe x16_4 slot support up to x8 mode.

Assuming I'm going to use all three 3.0 slots, would I be better off putting the 1080 in the second of the 3.0 slots (which is actually slot 3 of the four x16 slots)? Am I reading that right?

I don't know that the WiFi card or the RME card need 3.0x16 bandwidth, so they'd probably be fine in the x8 slots, or maybe one of them could even go in the 2.0 slot to allow me to run just two of the 3.0 slots at x16.

My head hurts now... ;)

Thoughts?
 
You would be right if you had 3 video cards (well, 3 x16 cards). But your WiFi card and the Audio card are x1 cards (assuming I looked them up correctly). I would put the video card in x16_1 (as recommended in the manual). Put the audio card in x1_2 and the WiFi in x16_4 (it will run as a x1 slot then).
 
Aug 7, 2018
2
0
10
They are indeed x1 cards, so they can both go anywhere, really. I guess what I'm asking though, is that it seems that by putting cards of any kind in the x16_1 and x16_4 slots, I'm forcing the x16_1 slot to run at x8 instead of x16. Is that not the case?