bottleneck performance?

[KarstenS]

Slot 1 16x - No GPU
Slot 2 16x - No GPU

You can put a GPU in either slot and have it work in 16x PCIe

PCI-E x16 slot doesn't mean it is connected with 16 lanes Read the data sheet carefully. Before I did my mobo update, I've read many of them. And all had something together: Not every slot can operate in x16 mode.

From my research, it typically looks like this:

Boards with 1 PCI-E x16 Slot the slot is typically connected with 16 lanes.

Boards with 2 slots that supports CorssfireX, slot 1 is connected with 16 lanes and slot 2 is connected with 4 lanes.

Boards with 2 slots that supports CrossfireX/SLI, slot 1 is connected with 16 lanes and slot 2 is connected with 8 lanes.

Boards with 3 slots (likeke my actual board) that supports ossfireX and SLI, slot 1 is connected with 16 lanes, slot 2 is connected with 8 lanes and slot 3 is connected with 4 lanes.

Boards with 4 slots that supports CrossfireX/SLI, as i could see, 2 slots are connected with 16 lanes and 2 slots are connected with 8 lanes. But if the slots with 8 lanes are filled, the slots with 16 lanes will operate in x8 too.

So if you need PCI-E at x16, you must put that card into a slot with 16 lanes and watch out to leave partner slots empty. Regular, there is also a warning in the manual to tell exactly this.

PCI-E 3.0 standard starts at x8. Its not fixed to x16

[Laraul]

PCI-E x16 slot doesn't mean it is connected with 16 lanes Read the data sheet carefully. Before I did my mobo update, I've read many of them. And all had something together: Not every slot can operate in x16 mode.

I've noticed a lot of confusion involving the number of lanes per slot, total number of lanes, etc. I do know that the maximum number of lanes is depends on the processor, split up between 4x, 8x, and 16x lane slots. In my case, I have four full size slots, the bottom two are 16 lane (slots 1 & 2), the top two are four lane (slots 3 & 4). That a total of 40 lanes, but placing two 16 lane cards into the bottom two (slots 1 & 2) disables slot 3, giving a total of 36 lanes. From what I can tell Xeon processors tend to have a higher number of available lanes. Usually 32-40 lanes on a Xeon versus 16 for an i7.

You can take a look at the manual for yourself. The PCI section starts on page 74. I do not know how the dividing up of lanes is done on other motherboards. The only way I know to determine what speed and how many lanes a slot is operating at is w/ software that tells me.

I personally haven't seen a noticeable performance difference between a card operating at PCIe 1.0 speed (2.5 GT/s or Giga-Transfers a second) and PCIe 2.0 speed (5 GT/s). PCIe 3.0 operates at 8 GT/s, though it increases efficiency effectively doubling the bandwidth versus PCIe 2.0. But w/o a noticable perception in performance difference, I find this discussion to be moot! IMHO.