How do I know if my PCIe lanes go through my chipset or directly to my CPU?

[fordongreeman]

In some motherboards, the PCIe lanes go through your chipset before it communicates to your CPU. But it's also possible (at least on high-end boards) for your PCIe bus to communicate directly to your processor without anything in between to slow it down.

This is important when using enthusiast GPU's to eliminate bottlenecks.

Is there any way of knowing if your board has this feature?

I have an Asrock Fatal1ty Gaming K6 Z370 enthusiast motherboard.

 

[Eximo]

Well, every chipset has a layout you can consult. However, motherboard manufacturers are free to re-configure the layout to anything they want.

Typically though, especially on Z class boards. The first x16 slot and the second x16 slot are hooked directly to the CPU. If you use a single GPU it will be 16x/0x all lanes going to the first slot. If you plug in a card in the other slot they will run in 8x/8x mode. Usually the second slot is only wired for 8x, so it can't run into 16x mode.

There might be a third x16 slot on many Z class motherboards, these are often 1x/4x/8x slots, rarely 16x, but this would go through the PCH and not directly to the CPU.

Some very expensive boards will have an additional PCIe switch and can do things like 8x/8x/8x for triple GPU configurations, though that is no longer common.

HEDT X class boards have more CPU PCIe lanes and their configurations vary a lot.

 

[Eximo]

In your case: - 3 x PCI Express 3.0 x16 Slots (PCIE2/PCIE4/PCIE6: single at x16 (PCIE2); dual at x8 (PCIE2) / x8 (PCIE4); triple at x8 (PCIE2) / x8 (PCIE4) / x4 (PCIE6))*

So the typical SLI/Crossfire capability. 16x/0x (Single GPU) 8x/8x (SLI/Crossfire) or 8x/8x/4x (Crossfire)