There was a time when for $279, just $20 more than what the Core i5-7640X asks, you could get a Core i7-920 processor, which gave you the full PCI-Express lane budget and triple-channel memory interface of the X58 high-end desktop (HEDT) platform, letting you drop in vast amounts of memory and 3-4 graphics cards. The i7-920 was one of Intel's iconic products and sold plenty. Since then, Intel got progressively stricter with their segmentation of its HEDT processors. With the Core X processor family, you now need to front at least $999 for the Core i9-7900X to be able to install 3-way or 4-way multi-GPU configurations. Every Core X SKU priced lower is limited to a 28-lane PCI-Express root complex, and then comes the Core X "Kaby Lake-X" family which is really the epitome of this point with a measly 16 lanes in total.

The Core i5-7640X is a tough sell given what we know. It does not really belong in the same discussion as the "Skylake-X" sector of Intel's HEDT platform in 2017 and is functionally more of a glorified Core i5-7600K with a negligible speed-bump, while maintaining the dual-channel memory interface and lower PCI-Express lane count. This means that some slots and onboard devices which were designed to work on even the 28-lane "Skylake-X" chips either downright won't work or work at crippled x1 bandwidth. To make things worse, this quad-core chip even lacks HyperThreading, making it the only HEDT processor, as of now, from Intel to do so. Add to that the meager 6 MB of L3 cache and loss of features introduced by the "Skylake-X" HEDT processors, such as mesh-interconnect and the Turbo Boost Max 3.0 technology, and the lack of integrated graphics in comparison to the i5-7600K, and this CPU comes off as the unloved stepchild of the family instead.

While this is not a fairy tale, there are some silver linings in the dark cloud. A strong usage-case for this chip is for overclockers, professional, or enthusiast who want to keep the least-expensive LGA2066 chip handy to achieve good results in low-threaded workloads or overclocking tests, and it could also be used for troubleshooting. We were able to overclock this chip to 4.90 GHz with ease, giving it a 16 percent performance boost. Also, the chip has sufficient performance to not bottleneck any high-end graphics card of the day and can power high-end gaming PC builds, but then, the same can also be said of the i5-7600K and 7700K. Similarly, if you've overshot your HEDT build budget, perhaps because of the current state of the GPU market, and are forced to go with a less expensive CPU today, with the plan to upgrade later, this could be the way to go. LGA2066 compatible motherboards do offer features and capabilities not available in the mainstream sector today. However, with both AMD and NVIDIA now prioritizing single-GPU performance, and dual GPU at most, 3-way and 4-way GPU configurations are getting rarer, which limits the use of HEDT for gamers. The lowest-priced LGA2066 motherboard costs around $200, versus Z270 boards starting at $100, which means that just to join the HEDT club with an i5-7640X (as opposed to the 7600K on Socket 1151), you'd have to shell out an extra $100 at least. If you planned on going entry-level HEDT now to buy a better CPU later, this cost has to be made up for. An alternative approach could be to buy Intel's mainstream platform today and sell it right before you have enough cash for the HEDT upgrade. Last but to least, there are AMD's Ryzen offerings which will shine under highly-threaded loads thanks to their higher core count - at similar pricing. However, their single-core performance lags behind that of Intel.

Tl;dr: The Core i5-7640X is in my opinion basically a 7600K (which is a quite decent product) that lacks IGP and sits on a socket that comes in at a $100 higher base price point for the platform itself.

The crux of the matter is that the justification of very specific situations and the begrudging acceptance of the status quo of the GPU market today is how everyone, including us, is making the Core i5-7640X look good. At its price point and after everything else has been taken into consideration, the i5-7640X leaves much to be desired, and we really can't recommend it to any serious HEDT platform buyers. If you only have $250 to spend on a CPU, it is better spent on a 6-core/12-thread Ryzen 5 1600X which, despite its MSDT platform, comes with 28 PCI-Express lanes from the processor and a lower motherboard-starting price. Another option are Intel's upcoming Coffee Lake processors, which were just announced and should be available real soon. We can only hope Intel is aware of the general disapproval of Kaby Lake-X and does not attempt to repeat this in the future.