Question ASUS Sabertooth 990FX R2, PCIe x16 slots speeds with single video card?

[LordWolf]

In the manual, it suggests using slot 1 for the video card, and then shows for slots 2, 3, and 4 as being x4, N/A, and x8 respectively.

So I'm wondering, if I'm using a different PCIe based card in those slots, how is the speed affected for them? Wouldn't make sense for them to not get x16 speeds (or whatever the max is for the card), ie, x4 in slot 2 as the max instead of the max of the card, or x8 speed instead of the max of the card. So can someone explain why it has those other speeds listed?

To clarify, I know that the max speed will never exceed that of the card (so won't get x16 with a card that is x4 max). So I'm not expect that. Just confused about what the chart means (in the manual it's on page 1-23). If I install other cards (not video cards) then I want to know how the system will function instead of coming across an issue and trying to figure it out. Thanks.

 

[kanewolf]

In the manual, it suggests using slot 1 for the video card, and then shows for slots 2, 3, and 4 as being x4, N/A, and x8 respectively.

So I'm wondering, if I'm using a different PCIe based card in those slots, how is the speed affected for them? Wouldn't make sense for them to not get x16 speeds (or whatever the max is for the card), ie, x4 in slot 2 as the max instead of the max of the card, or x8 speed instead of the max of the card. So can someone explain why it has those other speeds listed?

To clarify, I know that the max speed will never exceed that of the card (so won't get x16 with a card that is x4 max). So I'm not expect that. Just confused about what the chart means (in the manual it's on page 1-23). If I install other cards (not video cards) then I want to know how the system will function instead of coming across an issue and trying to figure it out. Thanks.

PCIe slots have a physical size and an electrical "size". The slot may physically hold an x16 card, but not all the pins in the slot are connected. The slot only has an electrical "size" of an x4 or an x8. The number of PCIe lanes in a motherboard are limited. They are usually pre-allocated by the motherboard manufacturer. In this case, the x4 comes from the motherboard chipset. IF the x8 slot is occupied, then the x16 from the first slot is split into two x8s to activate the additional slot.

 

[LordWolf]

Here is the basic version of the chart from the manual...

x16 Slots​	Slot 1​	Slot 2​	Slot 3​	Slot 4​
Single	x16​	x4​	N/A​	x8​
Double	x16​	x4​	x16​	x1​
Three way	x16​	x4​	x8​	x8​

So going based on what you said, it means that Slot 2 is physically x16 but electrically x4, correct?

What I'm wondering is this... do the same rules apply if the extra cards installed aren't video cards?