Intel gave its high-end desktop (HEDT) platform a much needed update this year with the Core X series consisting of 6-core, 8-core, 10-core, 12-core, and future 16-core and 18-core processors to cater to the pro-sumer crowd that just wants raw CPU power and platform connectivity without having to pay the Xeon tax (in exchange for reliability and ECC memory support). They've also brought PC enthusiasts the option of building future-proof rigs they don't have to upgrade for over half a decade.
Unlike previous generations of HEDT chips which were all positioned under a single Core i7 brand, Intel significantly changed its nomenclature. The "X" in the model number now denotes an HEDT model, one which features an unlocked base-clock multiplier, and the sub-brand itself has been expanded to include Core i7, the new Core i9, and even Core i5. As a general rule of thumb, SKUs with wide 44-lane PCI-Express interfaces are pushed up to the Core i9-79##X brand, while Core i7-78##X chips give you core-counts between 6 and 8 with 28-lane PCI-Express. These chips are built on the large "Skylake-X" silicon, which is a derivative of the "Skylake" micro-architecture, and feature significant architectural changes and not just linear increases in core counts over the mainstream desktop "Skylake-S" silicon.
In the wake of the AMD Ryzen 7 series bringing HEDT-like multi-threaded performance to the mainstream-desktop AM4 platform, Intel appears to have clearly panicked, rolling out the Core i5-7640X (which we are reviewing today) and the Core i7-7740X processors based on the "Kaby Lake-X" silicon. These chips are priced almost on-par with the LGA1151 Core i5-7600K and i7-7700K, and de-lidding by the community has shown that Intel basically placed the quad-core "Kaby Lake-S" die on the LGA2066 package to make these chips - but their only selling-point is their vertical upgrade path to larger multi-core processors.
The Core i5-7640X and i7-7740X have nearly the same stock clock speeds as their LGA1151 siblings, but their TDP has been bumped up to 112W from 91W, which many took as an indicator towards improved overclocking potential. Since the LGA2066 platform lacks onboard graphics, you lose out on the integrated graphics present on the "Kaby Lake" die, which could otherwise prove useful for troubleshooting. At the same time, you get the same dual-channel memory interface, meaning that half the memory slots on your socket LGA2066 motherboard won't function unless it happens to be one of the few boards designed only for Kaby Lake-X, which would have it support a dual-channel interface while having four slots in total; and you get all of 16 PCI-Express gen 3.0 lanes, which is only good for the amount of connectivity that would have you opt for the LGA1151 platform in the first place. As such, some expansion slots on your motherboard will either be disabled or run at much lower bandwidth with these chips.
In addition, the specs table below helps reveal more information. You lose out also on the silicon-level goodies Intel introduced with "Skylake-X", such as 1 MB of L2 cache per core, and the mesh-topology, which vastly improves inter-core communication while also reducing core-uncore latencies. As with the LGA1151 "Kaby Lake" chips, you only get 256 KB of L2 cache per core, the classic ring-bus topology, and even lose out on integrated graphics. As if that isn't worse, the Core i5-7640X even features a relatively small 6 MB of L3 cache and lacks HyperThreading. These are items that go beyond subjective reasoning; however, let us refrain on making a conclusion until all the tests are concluded and the results summarized.
To sum up, in this review, we put the Core i5-7640X, the $240 price of entry to the HEDT platform, to the test. We paired it with 16 GB of dual-channel memory and a GeForce GTX 1080 graphics card to see where Intel's Core i5-7640X stands in comparison to Ryzen and the LGA1551 Kaby Lake processors.