Intel Core i7-5820K CPU Is Nerfed, Has Crippled PCI Express Support

You would think that hardcore CPUs like the upcoming Haswell-E collection from Intel would have no trouble running a full quad-SLI or Crossfire NVIDIA/AMD multi-GPU configuration, and you'd be right. Unfortunately, there is an exception.

Specifically, one of the upcoming extreme-performance Core i7 central processing units has a crippled PCI Express support structure. Essentially, it possesses only 28 PCI Express lanes, instead of the full complement of 40 that the other two, as well as the “normal” Haswell high-end chip offer. Thus, the Core i7-5820K will actually have a poorer multi-GPU support than the Core i7-4960X Haswell central processing unit. To elaborate, the 28 PCI Express lanes have to divide bandwidth between all the populated PCI Express slots they are connected with. Because of that, not even PCI Express 3.0 x16 slots will run at full power. One will manage x16 performance, but the other will be limited to x8 mode. Also, the third slot will top at x4, while the four will not muster any bandwidth if you do install something in it while the other three are occupied.

It's a pretty far drop from the ability of the Core i7-5930K and i7-5960X to have two PCI Express x16 slots running full throttle while alongside a third slot with x8 mode. It's not exactly clear what Intel was thinking when it added this bizarre limitation to what, for all intents and purposes, should be the most overpowered platform available to consumers. Maybe the chips come out of the assembly line with a specific defect that affects the PCI Express root complex. Either way, keep this in mind if you're in the market for a Haswell-E CPU. At least you still get the six CPU cores and 12 MB L3 cache. It’s twelve logical CPUs, thanks to the HyperThreading technology. Needless to say, DDR4 memory is supported as well. And in the end, two video cards are more than enough for any setup, especially if they happen to be dual-GPU models.

Besides, the Core i7-5820K is pretty cheap compared to the other two, set to sell for $400 / €400 instead of the others' $1,000 / €1,000 and $600 / €600. A downside was to be expected. Last we heard, the Haswell-E line of central processing units was scheduled for launch on September 14, but we may see the things earlier, at IDF 2014 (September 9-11). Motherboards based on the X99 chipset and featuring the LGA 2011-3 socket are the only ones that can support the things.

Third best Haswell-E CPU ha crippled PCIe support
Image credits to Intel

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