Intel is reportedly giving final touches to a new line of high-end desktop processors under the Core i9 brand extension. Until now, the company used the Core i7 brand extension broadly, to cover both the top-end parts of the mainstream-desktop (LGA115x) segment, and the high-end desktop (HEDT) segment, consisting of the LGA1366 and LGA2011-series sockets. With the advent of the new LGA2066 socket, Intel will be launching two distinct kinds of products - the Core i7 "Kaby Lake-X" quad-core series; and the Core i9 "Skylake-X" 6-core, 8-core, 10-core, and 12-core processors.
The Core i7 "Kaby Lake-X" will include the much talked about Core i7-7740K and i7-7640K quad-core processors (there's no Core i5 Kaby Lake-X). These chips will feature up to 1 MB of dedicated L2 cache per core, which is four times that of the existing i7-7700K chip. The i7-7740K features 8 MB of shared L2 cache; while the i7-7640K features just 6 MB. Interestingly, the i7-7640K also happens to lack HyperThreading, while the i7-7740K features it. The i7-7740K will ship with higher clock speeds than the i7-7700K, with 4.30 GHz core, and 4.50 GHz Turbo Boost. The i7-7640K features 4.00 GHz core, with 4.20 GHz Turbo Boost. The Core i9 series is a whole different beast.
The Core i9 series will consist of four parts, the Core i9-7800X 6-core, Core i9-7820X 8-core, Core i9-7900X 10-core, and the Core i9-7920X 12-core. All chips feature HyperThreading, and 1 MB of dedicated L2 cache per core. The i9-7800X features 8,448 KB (8.25 MB) of shared L3 cache, and comes with clock speeds of 3.50 GHz core, and 4.00 GHz Turbo Boost. The i9-7820X eight-core chip features 11,264 KB (11 MB) of shared L3 cache, clock speeds of 3.60 GHz core and 4.30 GHz Turbo Boost. The Core i9-7900X ten-core chip features 14,080 KB (13.75 MB) of shared L3 cache, and clock speeds of 3.30 GHz, with 4.30 GHz Turbo Boost. Clock speeds of the top-dog i9-7920X twelve-core chip are unknown at the moment, but it comes with 16,896 KB (16.5 MB) shared L3 cache.
The i9-7800X, and the i9-7820X, along with the "Kaby Lake-X" based quad-core parts, feature 28-lane PCI-Express gen 3.0 root complexes, so your 2-card SLI/CrossFire setup will run at just x8 per card. The i9-7900X and i9-7920X feature 44-lane PCIe gen 3.0 root complexes, which enable the 3-way/4-way multi-GPU setups you originally bought any HEDT chip for. Further, the "Kaby Lake-X" quad-core parts feature just dual-channel DDR4 memory interfaces. The entire Core i9 "Skylake-X" series features quad-channel DDR4 memory interface. Socket LGA2066 motherboards will feature quad-channel wiring, with up to 8 DIMM slots, but when a Kaby Lake-X chip is installed, two memory channels are inactive.
Intel is expected to launch most of the Core i7 "Kaby Lake-X" and Core i9 "Skylake-X" lineup in June 2017, with the top-end i9-7920X following on in August, 2017.