Don't Waste Your Time (or Money)
Earlier this year when we were getting giddy for Ryzen, rumors began surfacing about how Intel might respond. At the time, we knew Ryzen would bring 6 and 8-core CPUs to the mainstream and it already looked as though Intel's quad-cores would be unable to compete. Granted, the 7600K and 7700K still look strong when gaming, but their time in the sun seems limited.
Along with preparing a series of Skylake-X processors, Intel's counter to Ryzen includes a Kaby Lake-X lineup consisting of the Core i5-7640X, which is basically a renamed 7600K, and the Core i7-7740X, a 7700K in disguise.
Leading up to their arrival, it was suggested that the 7640X might feature Hyper-Threading support, essentially making it a Core i7, while the 7740X would perhaps tout 6-cores. Those upgrades didn't seem particularly likely to me, and it also seemed improbable that Intel would release existing mainstream CPUs on their high-end desktop platform. After all, what would that achieve and how would this in any way be a counter to Ryzen?
Anyway that's exactly what Intel did, repackage its 7600K and 7700K Kaby Lake chips as Kaby-Lake X parts and call it a day.
On paper, you'll see that the Kaby Lake-X parts come with a mild factory overclock and sport a higher TDP while pricing remains the same. However, you can expect to spend more on a Kaby Lake-X build thanks to its pricier X299 platform.
It's hard to imagine why anyone would spend twice as much on an X299 board for these quad-core CPUs when they can get all the same features and capabilities in a Z270 board for half the price. Not only that, but half the features won't even work on the X299 boards when using a Kaby Lake-X CPU as they lack the required amount of PCIe lanes and only support dual-channel memory.
Setting that mess aside for now, let's move on to see whether the new Core i5-7640X and Core i7-7740X perform any faster than the familiar i5-7600K and i7-7700K...
Synthetic & Application Benchmarks
As mentioned, the Kaby Lake-X CPUs still only feature a dual-channel memory controller, unlike the Skylake-X parts such as the 7800X which boast quad-channel memory support. Unsurprisingly, when running DDR4-3200, we saw the same 31GB/s of memory bandwidth for the Kaby Lake-X parts as we did with the 7700K and 7600K.
The numbers in Cinebench R15 weren't unexpected. Despite their slight frequency advantage, the 7740X and 7640X are both only able to match the scores of their LGA1151 equivalents. At this point we largely know what we need to know, but I ran a heap of benchmarks anyway so we might as well check them out -- there are a few interesting numbers to note.
Take 7-Zip's figures for example: the 7740X managed to pull ahead of the 7700K yet the same can't be said for the 7640X versus the 7600K.
This time the 7740X was only able to match the 7700K in our Excel test while the 7640X falls behind the 7600K.
Moving to the PCMark 10 Essentials benchmark, the older mainstream Kaby Lake parts provide the best results here, narrowly outscoring newer Kaby Lake-X models -- a rather disappointing result for Intel's new high performance quad-core processors.
The 7700K and 7600K were again able to outscore the 7740X and 7640X, this time by a quite convincing margin in the productivity tests.
Something odd 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 double checked them.
The last PCMark 10 test simulated editing performance and here again the older Kaby Lake CPUs outpaced the 7740X and 7640X, albeit by slim margins.