Running Crossfire/SLI on LGA1156 boards

[Olo401]

Just wanted to mention this for those hardcore computer builders who have to run cards in Crossfire or SLI, because there seems to be a little confusion and/or misinformation going around..

Specifically, Warning: These P55 motherboards will cripple your Crossfire/SLI performance | Hardware Revolution

Here's what you need to know:

- Unlike the 1366 platform which has the PCI-E 2.0 controller on the X58 Northbridge chip, the 1156-based i5 and i7 CPUs have the controller built into the processor die to reduce latency (and as a precursor to Intel's upcoming Larabee GPU technology). However this on-die controller is only 16 lanes, instead of the 36 lanes on the X58 Northbridge. This means if you run two cards in Crossfire/SLI, each will run at 8x speed, Tri-GPU will run at 6x each, and so on.

- Even in the previous generation of Socket 775 boards, the lower-cost models (under $200) typically only include one slot that's enabled for PCI-E 2.0 16x. This has carried over to the lower-end 1156/P55 boards, because even now most people don't need Crossfire/SLI, or are budget gamers/enthusiasts who only run a single GPU, or will just purchase a X2 video card. You'll still see a second alternate-color PCI-E slot included on boards that aren't MicroATX size, which is set to run in 4x mode. Usually if you check the manual, packaging, or the specs on Newegg it'll mention this.

[Avanarius]

I honestly expected this anyways.

This is still similar to the P45 though it had the pci-e 2.0 controller built into the northbridge rather then the cpu.

You shouldn't cripple performance too much with a lower end card given the bandwidth of the 2.0 controller, but I wouldn't be putting a gtx 285 in sli or higher on this chipset. That would just be dumb.

[Amastacia]

Note also that this does not affect dual GPU solutions, only true multi-card SLI/CrossFire.

The 4870x2, for instance, has only 16 lanes externally facing the system. Even though there are 2 GPUs on board (and each, technically, has 16 lanes) there are only 16 lanes out.

Realistically speaking, the number of applications where CrossFire/SLI has an undeniable benefit is fairly small. So for all but a minute portion of the buying public (the ones running a 2560x1600 display and wanting all settings maxed all the time), the 16 lane restriction on the PCIe controller built into Lynnefield should not affect the buying decision.