If a 1x PCI-E expansions card gets plugged into a available 16x PCI-E slot will that drop the lanes down to 8x on the graphics card with this motherboard?
Yes. The reason is that the P5Q Deluxe does not have two 16X slots, it has one. The second slot is a supplementary 8X slot meant for a secondary video card, and it shares the 16 lanes with the first slot. When a card is placed into that slot, the motherboard will automatically split the 16 lanes between the two slots.
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