On May 30, chip giant Intel (NASDAQ:INTC) announced its new Core X series of processors for the high-end desktop personal computer market. In this lineup are two distinct series of processors: Kaby Lake-X and Skylake-X.

The Skylake-X parts come in variants with between six and 18 cores and are derived from the company's data center-oriented Xeon processors. The Kaby Lake-X parts come in quad-core configurations and are essentially Intel's mainstream Core i7-7700K and Core i5-7600K repackaged to work in the same motherboards that the Skylake-X parts do.

Intel's Core X processor.

Image source: Intel.

The Kaby Lake-X parts -- known as the Core i7-7740X and the Core i5-7640X -- are also a touch faster than their mainstream counterparts because Intel runs the former at slightly higher frequencies than it does the latter.

Based on a couple of useful data points -- the popularity rankings of these chips on Amazon.com (NASDAQ:AMZN) and Newegg.com -- it seems that the Kaby Lake-X chips aren't too popular with the "do-it-yourself" personal computer builder crowd.

Kaby Lake-X's unpopularity

On Amazon.com, the Core i7-7740X ranks 45th among the 100 most popular processor products on Amazon. Considering how readily available the 7740X is (Amazon.com indicates that the chip is in stock and ready to ship), and given that it's a new release, this isn't particularly good.

To be fair, the 7740X is more popular on Amazon.com than the higher end Core i9-7900X or even the Core i7-7820X -- two new, higher-end releases from Intel -- but the 7900X and 7820X have been out of stock on the website for quite some time, which will certainly have an impact on the popularity of those chips (Amazon's rankings are updated hourly).

The Core i5-7640X doesn't even show up in the top 100 processors on Amazon.com.

On Newegg.com -- another popular vendor of personal computer processors into the do-it-yourself market -- the 7740X is similarly unpopular. Among the 32 best-selling desktop processors on the site, the in-stock 7740X ranks 21st.

Again, the 7740X is "more popular" than the Skylake-X parts (7800X, 7820X, 7900X), but the higher-end 7820X and 7900X are sold out. To its credit, it is beating out the entry-level hex-core Skylake-X part, the Core i7-7800X.

And, unsurprisingly, the Core i5-7640X doesn't place among Newegg.com's top sellers.

Here's why it's unpopular

The Kaby Lake-X parts aren't bad processors. Their mainstream counterparts -- the Core i7-7700K and the Core i5-7600K -- are the two most popular processors on both Newegg.com and Amazon.com.

The problem that everyone seems to have (at least based on the several reviews of these chips that I've read) is that the platform costs associated with the Kaby Lake-X parts are significantly higher than those with the mainstream Kaby Lake-S parts.

I'll make it concrete for you. Here are the prices to put together systems based on Kaby Lake-S and Kaby Lake-X processors, respectively. Think of these as the minimum costs to get each processor up and running with all their features enabled (e.g., overclocking). Note that I am not gunning for feature parity -- just the bare minimum to get these processors into systems.

 Part

Kaby Lake-S System

Kaby Lake-X System

Processor

$310

$349

Motherboard

$109

$220

Memory

$71

$71

Total

$490

$640

Clearly, the Kaby Lake-S system is cheaper to get up and running while being virtually the same from a processor perspective (some websites reported better overclocking headroom for the 7740X versus the 7700K, but it's not a huge delta) due to both lower motherboard costs as well as lower processor costs, though the price reduction on the Kaby Lake-S parts seems to be a very recent -- possibly temporary -- development.

Another problem for Kaby Lake-X is that small form factor systems seem to be increasingly popular these days, and while there's a plethora of motherboards available for the Kaby Lake-S parts designed for small form factors (e.g., mini-ITX, Micro-ATX), there don't seem to be any such motherboards available today for the Kaby Lake-X parts.

Now, this isn't to say that there's no benefit to going with a Kaby Lake-X system over a Kaby Lake-S system for a computer builder. A system built around Kaby Lake-X is going to give the buyer many more potential upgrade paths (in fact, the Kaby Lake-S-based motherboards could be "dead ends" as far as future processor upgrades go), and there is the seemingly higher frequency potential of the 7740X over the 7700K.

At the end of the day, though, Kaby Lake-X looks to be off to a relatively muted start among the do-it-yourself crowd.

Ashraf Eassa owns shares of Intel. The Motley Fool owns shares of and recommends Amazon. The Motley Fool recommends Intel. The Motley Fool has a disclosure policy.