Aurora R8, GPU-Z reporting PCIe bus of only x8? #2

There's no replacement Dell board.  That's the way it was designed.  It's also the same design for the Aurora R7, R9, and R10.

Yes, x16 is theoretically twice as fast as x8. At PCIe 3.0, each lane is a little under 1,000 MB/s. So at x8 (3.0) you'd get maximum speeds a little under 8,000 MB/s, versus maximum speeds a little under 16,000 MB/s at x16 (3.0). In a real life scenario, I'm not sure it would make a large or even a noticeable difference in gaming performance.  The CPUs mostly are not going to be using that much bandwidth.  

@r72019 is correct. You find the same Dell small print in R10 spec.  And x8 works just as well as x16.  Maybe some of the saved PCIe lanes are used by NVMe PCIe ssd?

“From a quick look, there is a little below a 1% performance difference in PCI-e 3.0 x16 and PCI-e 3.0 x8 slots. The difference is not even close to perceptible and should be ignored as inconsequential to users fretting over potential slot or lane limitations.”

X8 in PCI-e 1.0 PCI-e 2.x PCI-e 3.0

x1 250MB/s      500MB/s      985MB/s
x4 1000MB/s    2000MB/s    3940MB/s
x8 2000MB/s   4000MB/s     7880MB/s
x16 4000MB/s  8000MB/s    15760MB/s

PCI-E 3.0 X8 has almost the same bandwidth as

 PCI-E 2.0 X16

https://www.pugetsystems.com/labs/articles/Titan-X-Performance-PCI-E-3-0-x8-vs-x16-851/