The release of Core i5 and i7 Lynnfield also meant the release of various motherboards with all one thing in common: The socket 1156.
If you look at the pictures of motherboards, you would believe that they are all at least equipped with two PCI-Express 16X ports. Let me explain where you might get fooled though.
What are you talking about?!
In order to cut on costs, on fourteen different motherboards, the second PCI-Express 16x is not connected via 8 lines to the PCI-Express controller of the LGA1156 processor (The first port then also being at 8x), but rather with 4 lines on the P55 controller.
On top of that, while the lines connected to the LGA1156 processor work at 5GT/s, the ones connected to the P55 only work at 2.5GT/s.
This result in a bandwidth of 1Gb/s in each direction for a PCI-Express 16x slot working at 4X with the P55 chipset, as opposed to 4GB/s when it’s working at 8x with the processor!
Needless to say, running Crossfire or SLI on a motherboard equipped with a 16x that works at 4x and is connected to the P55 chipset will cripple your performances.
Thank you to Hardware.fr (French website. I enjoy being bilingual 🙂 ) for reporting this.
The list of motherboards to avoid if you want to use Crossfire or SLI
Here’s a list of motherboards whose second PCI-Express slot is connected at 4X with the P55 and that I urge you to avoid if you plan to build a Crossfire or SLI system:
Asrock P55 Pro
Asrock P55M Pro
Asus P7P55D LE
Evga P55 Micro LE
The list of motherboards to go with if you want to use Crossfire or SLI
Here’s a list of motherboards that will not cripple your performance and run your video cards at 8X/8X with the LGA1156 processor controller. Note that no card needs 16X bandwidth yet, not even three Geforce GTX285 in Three-Way SLI.
They all support Crossfire and I indicate whether they support SLI or not.
I included a link to either NewEgg or Amazon when I could find them in stock at any of the two online stores.
ASRock P55 Deluxe (Two-Way SLI)
Asrock P55 Extreme (Two-Way SLI)
ASUS Maximus III Formula (Two-Way SLI)
Asus Maximus III Gene (Two-Way SLI)
ASUS P7P55 WS SuperComputer (Three-Way SLI, equipped with NF200)
ASUS P7P55D Deluxe (Two-Way SLI)
Asus P7P55D Premium (Two-Way SLI)
ASUS P7P55D PRO (Two-Way SLI)
Asus P7P55D EVO
If you have a blog, a website, Twitter account, Facebook, etc., I would deeply appreciate if you link to this story and spread the news. I would hate to see people buy a P55 motherboard without knowing this. I’m sure that you’ll agree 😉
I wish that manufacturers would make it more clear, but then again, it is up to the customer to double-check every information before making a purchase
As always, make sure to read all the specifications before buying any part and in the case that you have a doubt, consult with experts 😉