*
Only a problem if you use 2 * graphics card running in PCi-e X16 because this card use PCI-e X4
not a big problem your graphic card running after in X8 mode
(Note 3) The PCIEX8_1 and PCIEX8_2 slots share bandwidth with the PCIEX16_1 and PCIEX16_2 slots respectively. When PCIEX8_1 is populated with an expansion card, the PCIEX16_1 slot will operate at up to x8 mode; when PCIEX8_2 is populated with an expansion card, the PCIEX16_2 slot will operate at up to x8 mode.
Actually I think you are mistaken here Pierre. This is the UD9 board and they have more X16 slots and more X8 slots. Here is the relevant part from the manual:
(Note 2) For optimum performance, if only one PCI Express graphics card is to be installed, be sure to
install it in the PCIEX16_1 slot; if you are installing two PCI Express graphics cards, it is recommended that you install them in the PCIEX16_1 and PCIEX16_3 slots.
(Note 3) Each PCIEX8 slot shares bandwidth with the corresponding PCIEX16 slot (PCIEX8_1 with PCIEX16_1, PCIEX8_2 with PCIEX16_2, and PCIEX8_3 with PCIEX16_3). When a PCIEX8 slot is populated, its corresponding PCIEX16 slot will operate at up to x8 mode.