PCI-E 2.0 link @x8 on ASUS P7P55D Deluxe

[ntsarb]

Similar issue here:

I have 2x Nvidia GTX 660 (MSI Twin Frozr) on SLI setup, plugged onto an ASUS P7P55D-E EVO mobo.

One of the graphics cards operate on PCI-E x4 2.0 and the other on PCI-E x8 1.1 !!!

The mobo should support PCI-E @ x16 for single card configuration, or x8 for dual card configuration (SLI), according to the following:
http://www.asus.com/Motherboards/P7P...specifications

Is there any configuration option that would allow switching both PCI-E to x8 2.0?

Update:
Following some research for information on the web, I found an article (see below) suggesting that the Intel P55 chipset, which was used on many motherboards, limits the bandwidth of the PCI-E 2.0 bus down to 2.5GT/s per lane, hence providing the same bandwidth as PCI-E 1.0.

http://techreport.com/review/17513/i...xpress-chipset

The same issue is verified by another user, on an MSI p55-gd65 motherboard:
http://forums.anandtech.com/archive/...t-2228353.html

My understanding is that this is where the problem is. ASUS's web site and product documentation claims that the motherboard supports one of single PCI-E 2.0 x16 slot or dual PCI-E 2.0 slots at x8/x8 mode. GPU-Z measures half that: The actual performance of the PCI-E bus is PCI-E 1.0 x8 (i.e. half of PCI-E 2.0 x8), or PCI-E 2.0 x4 (i.e. half of PCI-E 2.0 x8).

I have informed ASUS technical support, requesting them to correct the documentation of their motherboards, to clearly specify the PCI-E performance that is supported by their boards.

Update (26/08/2013):

On 19 August 2013, I received the following response from ASUS:

"Thank you for your feedback, I am take your feedback to our relative department."

Very disappointing, really. They have not fixed the errors in the specs of the board. I used to be an ASUS customer for many years, from now on I will have to avoid them.