Running A PCIe x16 Graphics Card in PCIe x8 Slot

Further to our look at AGP vs PCIe I am also looking at the impact on the output of the GPU due to the PCIe slot used.
Normally a GPU is run in a PCIe x16 Slot but on some motherboards you may only have a PCIe x8 slot.

Will Your graphics card run? Well the answer is yes but does it impact the performance of your card?

PCIe comes in 5 Generations to date and a 6th in the pipeline.

PCI EXPRESS SPECIFICATIONS

GEN	YEAR	RATE	X1	X2	X4	X8	X16
PCIe 1.0	2003	2.5 GT/s	250 MB/s	0.500 GB/s	1.00 GB/s	2.00 GB/s	4.00 GB/s
PCIe 2.0	2007	5.0 GT/s	500 MB/s	1.000 GB/s	2.00 GB/s	4.00 GB/s	8.00 GB/s
PCIe 3.0	2010	8.0 GT/s	984.6 MB/s	1.969 GB/s	3.94 GB/s	7.88 GB/s	15.75 GB/s
PCIe 4.0	2017	16.0 GT/s	1969 MB/s	3.938 GB/s	7.88 GB/s	15.75 GB/s	31.51 GB/s
PCIe 5.0	2019	32 GT/s	3938 MB/s	7.877 GB/s	15.75 GB/s	31.51 GB/s	63.02 GB/s
PCIe 6.0 (Planned)	2021	64.0 GT/s	7877 MB/s	15.754 GB/s	31.51 GB/s	63.02 GB/s	126.03 GB/s

PCIe 3.0 is currently the most common for GPU's at the moment and there has been some test done indicating that running a PCIe 3.0 x16 GPU in an PCIe 3.0 x8 slot wont hamper its performance much if even at all.
So that indicates the average PCIe 3.0 GPU requires less than 8000 MB/s to operate to its full capacity.

So we have learned so far that you can run a PCIe 3.0 x16 GPU in an PCIe 3.0 x8 Slot!
Great most will be happy here but what about older generation boards how does using a PCIe 2.0 slot affect a PCIe 3.0 GPU?
With PCIe 2.0 x16 running at around 8000 MB/s again it doesn't hamper performance as its similar to PCIe 3.0 x8.

• Well how low can we go?
• What does the average PCIe 3.0 GPU actually require?
• Will it run on a PCIe 2.0 x8 slot running at about 4000 MB/s which is half of PCIe 2.0 x16 and PCIe 3.0 x8?

The PCIe 3.0 GPU's In Question are mainly Nvidia GTX 1050Ti 4GB & AMD Radeon RX570 4GB but also am using the following for testing which is Nvidia GTX 760 2GB (Its better for GPU processing than the 1050Ti 4GB! - At least until I get something better...)

Well lets find out and let the testing begin...