Gigabyte GA-H67MA-UD2H: 2x PCIe 16x or 2x PCIe 8x?

[Synomenon]

I have a Gigabyte GA-H67MA-UD2H. It has two PCIe 16x slots. I think the second one is 4x only (I only see traces through part of the length of the slot).

If I put anything in this second 16x slot, will the first 16x slot drop down to 8x speed?

 

[combust3r]

That isn't very clear at the moment but AFAIK no, only supported mode is x16/x4 not x8/x8 as many reviewers thought.

 

[coffeejunkee]

H67 is limited to x16. Only P67 offers x8/x8 (although the cheaper boards are x16/x4).

The first slot always runs at x16 and is connected to the pci-e controller inside the cpu. The second slot always runs at x4 and is connected to the southbridge (and then by dmi to the cpu).

 

[MagnusTheBrewer]

The important aspect is that you will see no difference between 16x, 8x and, 4x, in regards to video performance.

 

[yottabit]

At first I was going to say "Performance with a graphics card in the x4 slot will be miserable" because I thought it would run at PCI-e 1 speeds like all the P55 chipsets, but looking at the specs on the H67 it looks like it runs PCIe 2 speeds so that x4 slot is actually a PCIe 2 slot (or PCIe 1 8x equivalent)

That should be adequate for most non-monster cards but I'm not sure how it plays in a dual gpu configuration since it has to go through the northbridge vs. the other card which has a direct link... I've heard of issues with stuttering and the like but I don't know how much credibility are behind them.

You WILL see a performance hit on a PCIe 2.0 x4 using a very high end graphics card. This will only get worse as they get faster and faster . But for all the midrange right now the performance hit should be minor

 

[yottabit]

Performance should be comparable to a x4 slot on an X58 board as tested by toms here:
http://www.tomshardware.com/reviews/p55-pci-express-scaling,2517-6.html

So on average a 12% drop with a 5870 using the PCIe 2 x4 slot

Dropping to P55 PCIe "1" x4 Slot hits performance 30%

 

[coffeejunkee]

I decided to check to specs on giga site, just in case.

It says under Multi-Graphics Technology:

Support for ATI CrossFireX™
* The PCIEX16 slot operates at up to x8 mode when ATI CrossFireX™ is enabled.

Now I don't understand why this would be. The H67 chipset diagram is pretty clear, 16 lanes coming from the cpu and 8 lanes from the ich. Why the pci-e x16 slot would be reduced to x8 if I put in a card in the other slot is not clear to me.

Possibly the site has incorrect information. Probably best to ask gigabyte themselves.

 

[yottabit]

I decided to check to specs on giga site, just in case.

It says under Multi-Graphics Technology:

Support for ATI CrossFireX™
* The PCIEX16 slot operates at up to x8 mode when ATI CrossFireX™ is enabled.

Now I don't understand why this would be. The H67 chipset diagram is pretty clear, 16 lanes coming from the cpu and 8 lanes from the ich. Why the pci-e x16 slot would be reduced to x8 if I put in a card in the other slot is not clear to me.

Possibly the site has incorrect information. Probably best to ask gigabyte themselves.

I'm guessing that is wrong information. That would make sense for boards that do a x8 x8 split, which is actually a better solution for crossfire than the x16 x4.