Intel Kaby Lake-X Evaluation: Core i7-7740X & Core i5-7640X

Earlier this year, when we got dizzy for Ryzen, rumors surfaced about how Intel might react. At the time, we knew that Ryzen would bring 6 and 8 core CPUs into the mainstream, and it already looked like Intel's quad cores couldn't keep up. Granted, the 7600K and 7700K still look strong when playing, but their time in the sun seems to be limited.

In addition to preparing a line of Skylake-X processors, Intel's Ryzen counter includes a Kaby Lake-X line that consists of the Core i5-7640X, which was basically renamed 7600K, and the Core i7-7740X, a clad 7700K , consists.

Before their arrival, it was suggested that the 7640X could offer hyper-threading support, essentially making it a Core i7, while the 7740X might announce 6-cores. These upgrades didn't seem particularly likely to me, and it also seemed unlikely that Intel would release existing mainstream CPUs on its high-end desktop platform. After all, what would that do and how would it counteract Ryzen in any way?

That's exactly what Intel did: repack the 7600K and 7700K Kaby Lake chips as Kaby Lake X parts and name it a day.

On paper, you'll see that the Kaby Lake-X parts come with a mild factory overclock and have a higher TDP, while prices stay the same. However, thanks to the more expensive X299 platform, you can expect to spend more on a Kaby Lake-X build.

It's hard to imagine why someone would spend twice as much on an X299 card for these quad-core CPUs if they could use all the functions and capabilities of a Z270 card at half the price. In addition, half of the functionality does not even work on the X299 cards when using a Kaby Lake X CPU because they lack the required number of PCIe lanes and they only support two-channel memory.

Let's put this mess aside and see if the new Core i5-7640X and the new Core i7-7740X work faster than the familiar i5-7600K and i7-7700K …

Synthetic & application benchmarks

As already mentioned, unlike the Skylake-X parts like the 7800X, which support quad-channel memory, the Kaby Lake-X CPUs still only have a two-channel memory controller. Not surprisingly, when we ran DDR4-3200, we saw the same 31GB / s memory bandwidth for the Kaby Lake-X parts as for the 7700K and 7600K.

The numbers in Cinebench R15 were not unexpected. Despite their low frequency advantage, both the 7740X and 7640X can only achieve the values ​​of their LGA1151 equivalents. At this point, we mostly know what we need to know, but I still did a lot of benchmarks so we can check them as well – there are a few interesting numbers to consider.

Take, for example, the numbers from 7-Zip: The 7740X prevailed over the 7700K, but the same does not apply to the 7640X compared to the 7600K.

This time the 7740X could only keep up with the 7700K in our Excel test, while the 7640X lags behind the 7600K.

In the PCMark 10 Essentials benchmark, the older mainstream Kaby Lake parts deliver the best results and only marginally outperform the newer Kaby Lake-X models – a rather disappointing result for the new high-performance quad-core processors from Intel.

The 7700K and 7600K again outperformed the 7740X and 7640X, this time with a pretty convincing lead in productivity tests.

Something strange is happening here. The 7740X and 7640X were significantly slower for the photo editing test, and I'm not sure why. These results don't really make sense, but I can assure you that I checked them again.

The last PCMark 10 test simulated machining performance, and again, the older Kaby Lake CPUs outperformed the 7740X and 7640X, albeit slightly.

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