The main difference between the Intel i7-5820K and the i7-5930K, besides the minor clock difference, is the number of PCIe lanes it can address.  The lower specced model can steer up to 28 PCIe lanes, while the more expensive i7-5930K can handle up to 40 PCIe lanes. This implies that the 5820K is only capable of handling triple GPU setups and the Quad SLi/Crossfire is only supported by the 5930K and 5960X Haswell-E models.

Initially we wanted to test a triple GPU setup, sadly one HD7970 card has bitten the dust and was erratic in performance. So we are limited to a dual 7970 GPU Crossfire setup, though the outcome is crystal clear and as expected.

All processors were overclocked at 4GHz, to even the playing grounds more the memory speeds were also limited this at 2666MHz.

• For the DDR3 platforms: 2666C10-12-12-35 Command Rate 2T

• For the DDR4 platform: 2666C15-15-15-35 Command Rate 2T

The Firestrike Extreme benchmark from Futuremark is a real GPU crusher, though it becomes clear that there is no huge difference between the two six core Haswell-E processors. With the i7-5820K one 7970 was running at X16 speeds while the second card was running at x8 speed. For the more expensive i7-5930K both 7970 cards were running at X16 PCIe 3.0 speeds. In their latest version Futuremark also included a 4K test (3840x2160 resolution), baptized Firestrike Ultra, their most demanding benchmark ever till date. Here the differences are even smaller, hence which makes us conclude that most users will not even notice the difference between a GPU running at X8 speeds or when running full blast at X16 speeds. Synthetic benchmarks will reveal a small discrepancy, though for gamers  it will hardly be a big deal.

The synthetic tests reveal a small difference, though once looking at our three game tests, which were cranked up to run at the maximum possible resolution plus detail preset, the difference is within the margin of error.