In the book and I was looking at the bios and not this. If you look at the bottom it will tell why it work. When you were trying that card in the 3.0 slot it wouldn't work. The card is maybe like a 1.0 or 2.0 card. When you put into the 2.0 slot than it work.
Expansion Slots 1 x PCI Express x16 slot, running at x16 (PCIEX16) * For optimum performance, if only one expansion card is to be installed, be sure to install it in the PCIEX16 slot.
1 x PCI Express x16 slot, running at x8 (PCIEX8)
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. It will operate at up to x8 mode when the PCIEX16 is populated.
2 x PCI Express x16 slots, running at x4 (PCIEX4_1, PCIEX4_2)
* The PCIEX4_1 slot shares bandwidth with the PCIEX16 and PCIEX8 slots. When it is populated, the PCIEX16 slot will operate at up to x8 mode and the PCIEX8 slot will operate at up to x4 mode.
* When installing a x8 or above card in the PCIEX4_1 slot, make sure to set PCIE Slot
Configuration in BIOS Setup to x4. (Refer to Chapter 2, "BIOS Setup," "Peripherals," for more information.)
(The PCIEX16, PCIEX8, and PCIEX4_1 slots conform to PCI Express 3.0 standard.)
1 x PCI Express x1 slot (The PCIEX4_2 and PCIEX1_1 slots conform to PCI Express 2.0 standard.)