Won't find that in BIOS (I think), try
GPU-Z.
(Under "bus interface", it will say how many lanes it's "@". Motherboards with PCI-E have a limited number of lanes; generally the 2nd PCI-E 16x slot has 8 lanes, and the primary switches to 8x as well when the secondary is occupied. Make sure you always put a graphics card in primary and keep the secondary empty. One of the smaller 4x or 1x slots is fine for audio.)
Light might just be because of low RPM. My old Asus board used to complain about CPU fan failure on each boot, but it was just spinning really slowly.