It will please overclockers, but lets the features of compatible motherboards go to waste
THE REVEAL OF Intel’s latest round of premium enthusiast CPUs – based around the new X299 chipset – was a bit of a break in tradition. In addition to the expected top-end Skylake-X platform, which ranges from the six-core Core i7-7800X to the 10-core Core i9-7900X, we have Kaby Lake-X, consisting of the relatively affordable quad-core Core i5-7640X and Core i7-7740X.
These seem to share silicon from the standard 14nm Kaby Lake family, albeit tweaked for enthusiast use. The Core i7-7740X we were provided with, for instance, comes in at about the same price as the Core i7-7700K, but has a slightly higher base clock speed of 4.3GHz (the Turbo Boost clock is the same at 4.5GHz), a higher 112W TDP and expanded voltage and frequency windows for overclocking. Integrated graphics are gone as well, since Intel intends for it to be paired with a dedicated graphics card.
LAKESIDE BY SIDE
With these modifications, you might think that the Core i7-7740X would at least edge ahead of the Core i7-7700K in benchmarks. While they do indeed come out very close, the Core i7-7740X’s overall score of 159 is actually four points lower than the older Kaby Lake’s. The newer CPU wins out in the image test, scoring 146 to the i7-7700K’s 142, but falls very behind in the video and multitasking segments, scoring 151 and 168 – to the Core i7-7700K’s 174 and 163 – respectively.
There won’t be much of a perceptible difference in day-to-day use, but it’s slightly odd that Intel should bring out a chip that essentially matches an existing product on price, core count and stock-speed performance. Even overclocked to 4.7GHz, the Core i7-7740X’s overall score only reached 163, compared to the Core i7-7700K’s 170.
That said, overclocking is also where the Core i7-7740X starts to show its worth. The highest we could push our Core i7-7700K to without crashing or significant throttling was 4.7GHz, but with the same Cooler Master MasterLiquid 240 AIO cooler, the Core i7-7740X can go all the way up to 5.2GHz, with the only cause for concern being occasional temperature spikes to 100°C. Nonetheless, it remained stable, and produced a superior overall score of 176, as well as a much- improved multitasking score of 186.
Overclocking this far also made for a decent improvement in the Dirt Showdown benchmark. Due to the lack of integrated graphics, we ran this using an Nvidia GeForce GTX 1060 GPU, and saw its average frame rate (at 1080p with Ultra settings) rise from 108fps at Intel’s stock speeds to 124fps at 5.2GHz. We also tried the Radeon R7 260X, with which it produced 84fps at both CPU clock speeds.
Metro: Last Light Redux didn’t see much of an effect, though – probably since in this game, the GPU is more likely to act as the bottleneck than the CPU. Only a single frame was gained by overclocking to 5.2GHz with the GTX 1060, going from 41fps to 42fps.
Still, there are other advantages over the Core i7-7700K. We found the standard Kaby Lake CPU worryingly easy to max out its core temperatures, but despite the Core i7-7740X’s higher power consumption, it seems to stay much cooler: at stock speeds, it idled at 34°C, generally stayed around the 68°C area during load and only peaked at 76°C. The Core i7-7700K, by contrast, hovered at around 85°C under load and peaked at 100°C, even though its idle temperature was the same.
The Core i7-7740X does exceed these at 5.2GHz, idling at 36°C and hitting 95°C under load with occasional peaks to 100°C, but for peace of mind you could always dial it back to 5GHz instead. This only results in an overall benchmark score of 171, but its load temperature of 70°C and peak of 90°C are much better for the CPU’s health, assuming it’s going to be put under pressure that often.
This combination of cooler running and higher overclock potential means that, other things being equal, the Core i7-7740X is the better choice. Unfortunately, all other things are not equal. Because it uses both a new chipset and a new socket, LGA 2066, you’ve no choice but to buy a new motherboard as well, and X299 models are – like their X99 predecessors – significantly more expensive than even a really good Z270 model for Kaby Lake. You’re looking at minimum, which is over more than the Best Buy-winning MSI Z270 Tomahawk Arctic.
The worst part is that with Kaby Lake-X, you can’t take full advantage of the X299’s feature set. The reason these motherboards cost so much is a combination of their support for 8-slot, quad-channel RAM, the huge assortment of PCI-E slots, and things like the ability to run multiple graphics cards at full x16 speeds instead of dropping to x8.
The Core i7-7740X, however, only supports dual-channel RAM, rendering half the DIMM slots useless, and its 16 PCI-E lanes is no improvement over the standard Kaby Lake platform. Intel says that cheaper X299s with dual-channel RAM and fewer PCI-E slots could be released at lower prices, but until then, you’re paying for hardware you can’t use.
Lastly, there’s the red team. AMD’s Ryzen 7 1700 is about cheaper than both the Core i7-7700K and i7-7740X, but thrashes both in our benchmarks, scoring 186 at the stock speed of 3GHz. It also has twice the cores, twice the threads and eight more PCI-E lanes. It also only supports dual-channel RAM, but is a more fitting purchase for highend PCs (besides those specifically for gaming, where both Intel chips are better suited).
Alternatively, there’s the Skylake-X Intel Core i7-7800X. It costs not much more than the Core i7-7740X, but is a real enthusiast CPU, with six cores, 12 threads, a full 28 PCI-E lanes and quad-channel memory support.
SOCKET LGA 2066 • CORES 4 • FREQUENCY (BOOST) 4.3GHz(4.5GHz) • INTEGRATED GRAPHICS None • WARRANTY Three years RTB • PART CODE BX80677I77740X