Gigabyte GA-Z87-HD3 motherboard and PCIe slots sharing lanes?

[RJSmith92]

Hello,

 

I was reading the Spec for the GA-Z87-HD3 and it says -

 

 

When it says - "The PCIEX4 slot shares bandwidth with all PCI Express x1 slots. All PCI Express x1 slots will become unavailable when a PCIe x4 expansion card is installed."

 

Does this mean that if I plug any card into the x4 slot that both the PCI Express x1 slots won't work or only if I plug a x4 into that slot?

 

For example if I put a x1 card into that slot would I still be able to use both the x1 slots?

 

Also, when it says that they "share bandwidth" does that mean that they share the same physical lanes between the slots? and when you put a card in (e.g. into the x4 slot) it cuts of the lanes reaching the slots further down?

 

Any help would be appreciated,

Thanks

[mapegl]

Think of it this way. you have 4 lanes for pcie 1x and 4x slots. priority is the 4x slot, so if 4 lanes are used there, they are gone and no 1x slot is available. if you use a 1x card in the 4x slot, you still have 3 lanes left and therefore enough for the other 1x slots.

 

i hope that makes sense.

 

your 16x slot is not affected since it has its own 16 lanes....

[RJSmith92]

Think of it this way. you have 4 lanes for pcie 1x and 4x slots. priority is the 4x slot, so if 4 lanes are used there, they are gone and no 1x slot is available. if you use a 1x card in the 4x slot, you still have 3 lanes left and therefore enough for the other 1x slots.

 

i hope that makes sense.

 

your 16x slot is not affected since it has its own 16 lanes....

 

Thanks a lot for this reply. Yes it makes sense and is what I would have thought 

 

I asked this question on another forum and got a flat out "No, you won't be able to use the x1 slots even if you have x1 card in the x4 slots", which I didn't think was right.

 

So this correct - "Also, when it says that they "share bandwidth" does that mean that they share the same physical lanes between the slots? and when you put a card in (e.g. into the x4 slot) it cuts of the lanes reaching the slots further down?"

 

Thanks.

[Faa]

The source of the lanes for the 1st slot and all the other slots are different. 1st slot is complety from the CPU and all others are from the southbridge which you have 4x lanes@PCIE 3.0 or 8x@PCIE 2.0 in total.

Crossfire is possible, SLI not.

[mapegl]

Problem here being that the 4x slot is only PCIe 2.0. This actually decreases performance for crossfire. If it was a PCIe 3.0 4x this would not really be a problem.

 

So crossfire with high-end cards is not really the best here. Medium-range cards should not have a problem there.

[RJSmith92]

Thanks for the replies.

 

I'm not actually wanting to use Crossfire, I just have a single GPU in the x16 slot.

 

My question was just really regarding the 4 free lanes from the ICH. It looks like there are only 4 lanes to the PCIe switch, but from the switch there are 6 lanes (1 for each x1 slot and 4 for the x4 slot) and the switch controls access based on what is in the x4 slot as the image below suggests -