Strange Duck this Gigabyte R7-260 video card

I asked for suggestions for a video card on an earlier post Graphics card suggestions please
and decided to purchase a Gigabyte R7-260x (PCIe 3.0), knowing it was overkill for my intended purpose; but having the necessary plug-ins..
The Intel board I wanted it for was a PCIe 2.0 and the new card was a 3.0 (exchangeable according to conventional wisdom). The Intel wants nothing to do with it.
I reinstalled the Sapphire HD 4850 (PCIe 2.0) that I had taken out of the Intel and it was immediately detected and ran fine. To proof it, I put an older MSI R 4550 HD (PCIe 2.0) into the Intel and it also worked fine.
Thinking the Gigabyte R7-260x may be faulty, it was put in a Gigabyte board with PCIe 2.0 and it worked fine.. Video card is OK!
All the BIOS settings have remained the same through the tests. It seems the Intel just does not like the Gigabyte R7-260x, unless the "strange duck" needs some special enticement to kick its butt?

Thanks Stormy for the reply. Kinda figured I was correct in my assumption.
Will just use the R7 260x in something else and maybe replace the old Intel board.

Cheers! :)