Question about PCIE Gen Setting

Souths1der wrote: I'm having an issue with a riser cable.  While I know it's an issue with the riser cable, the solution to make it work is changing a setting in the BIOS.  I'm curious what the ramifications are in the setting I need to make my  video card work. I have  Thermaltake P5 case and I bought it because I like the looks of the video card being mounted vertically.  To do that you have to use a riser cable.  The following issue happens with their supplied riser (a known issue at Thermaltake) and a high quality 3M riser I purchased while troubleshooting.  With the riser plugged into PCIE1 and the BIOS setting for that slow set to Auto, Gen3, or Gen2 I get no video from my card.  My card only works with the setting at Gen1.  This problem exists with both the above cables and two different video cards (R9 390X and GTX 1070). I know that the settings probably have no effect on gaming performance, etc.  I've read all those tests.  However, I also do some overclocking, and need to get every last clock.  So I'm curious what is actually happening to the communication through that slot with the setting at Gen1.  Is it no longer communicating at x16 but at x8 or x4?  Is it still running at max Gbps?  This information is what I can't seem to find anywhere. Thanks in advance for any info you can provide.

IF you are still wondering about this, which has been answered above, at least IMO it has, I'll repeat it in my words.

The answer is bandwidth or speed of the interface is lower in Gen1 mode (PCIe 1.0), than it is in Gen2 mode (PCIe 2.0) or Gen3 (PCIe 3.0.) So no, it is not still running at the maximum Gbps in Gen1 mode.

Given this, the affect on gaming performance is obvious, up to a point. Normally a Gen3/PCIe 3.0 x8 connection will be more than any video card can use. With new video cards, 4K displays, and VR, that may no longer be true.

The number of PCIe lane connections, x16, x8, etc, is not changed at a Gen1 setting, or any setting of that option.

The need to set the PCIe connection to Gen1/PCIe 1.0 speed when using the TTake riser cable seems to indicate it is so cheaply made, or were defective from the factory. But since the 3M cable did the same thing, it makes me wonder. The thought of the CPU trying to maintain Gen3 bandwidth through a riser cable, which likely more than doubles the length of the connection to a video card, does not inspire confidence IMO.

I forget what board you are using, and I don't see that information in this thread.