Intel Kaby Lake Benchmark – The i7-7500U tested in the Asus Zenbook 3
Last summer, Intel announced its new processor generation: Kaby Lake. It is the successor to Skylake and should, of course, be faster than its predecessor. As with previous processor generations, the chips for laptops and convertibles, with TDPs from 4.5 to 15 watts, will be available first and Intel will release faster (quadcore) chips for laptops and desktops in early 2017.
We already published a background article about the architecture of Kaby Lake in August , but in the meantime we have also been able to run benchmarks on a Zenbook 3 from Asus. We were not yet allowed to review the laptop itself, because it is not yet a ‘finished’ copy, so unfortunately we still have to wait for a full review of the Zenbook 3.
Benchmarking
So we were able to run processor benchmarks on the laptop, which is equipped with a Core i7-7500U processor. It is a dual-core CPU with a clock speed of 2.7 GHz and a turbo frequency of 3.5 GHz. It is the successor to the Core i7-6500U, which ticks at 2.5GHz and has a maximum turbo clock of 3.1GHz. The architecture of the processor has not changed since Skylake, but because Intel has improved its 14nm process, Kaby Lake has become more efficient and the clock speed could be increased while the energy consumption remained the same.
Skylake’s HD520 GPU has been replaced by the HD620 GPU at Kaby Lake, the clock speed of which is unchanged, but the mfx engine has been modified. It now supports decoding 10-bit HEVC video at 4K resolution. We’ll look at that later in this article, but we’ve started running our usual benchmarks.
Immediately with the first result in Cinebench 15 Multi, we already came to a striking result; the 7500U is slower than the 6500U processors in previously tested laptops. We no longer had the Specter x360 and Zenbook UX305UA on hand, so couldn’t compare, but we suspect the cause lies in temperature and power management.
When we started Cinebench Multi and monitored the CPU’s behavior with the Intel Power Gadget, the CPU consumed more than its tdp during the first 20 seconds of the benchmark. The clock speed on both cores rose to 3.3 GHz, but after those twenty seconds the consumption dropped to 15 watts and the clock speed remained between 2.8 and 2.9 GHz. We assume that the Specter x360 and the Zenbook UX305UA were able to run at their maximum clock speed longer than the Zenbook 3, which accounts for the higher score in Cinebench Multi.
If that limitation due to the power management is absent, Kaby Lake in the Zenbook 3 turns out to be faster than Skylake. In Cinebench Single only one thread is used, which can run at the maximum clock speed of 3.5GHz. The Intel Power Gadget indicates that consumption, at about 13 watts, remains within limits and the result is an almost 12 percent higher score than the Specter x360. Although in these benchmarks it seems that Kaby Lake is slower than Skylake, that is not necessarily the case. The performance of the Intel processors is increasingly dependent on the laptop’s power management and in some cases also on the cooling, if it is deficient. We will probably test even more laptops in the future that also outperform Cinebench Multi Skylake.
We not only ran Cinebench, but also 3DMark, in which the results are in line with those of Cinebench. The 3DMark scores are broken down into an overall score, one for graphics and one for physics. The physics part relies heavily on the CPU cores, which already had a hard time in Cinebench Multi. In the graphics part, more is asked of the GPU and the Zenbook 3 scores high again.
Finally, we ran three self-developed benchmarks in Lightroom, Handbrake and Photoshop CC. The Kaby Lake processor is at the top of the list in most cases, but always has to give way to the HP Specter. As mentioned, this doesn’t mean that Kaby Lake is slower than Skylake; it mainly means that the Zenbook 3 as we tested it has a somewhat stricter power management than the tested Specter x360.
Hevc video
If Kaby Lake can fully exploit its turbo speed, the processor is faster than Skylake, but that result is due to the higher clock speed. The gpu cores have not been tinkered with either, but Intel has made adjustments to the mfx engine. It now supports decoding 8 or 10bit vp9 and 10bit hevc video. Vp9 is used on YouTube, among others, and hevc is the standard for UHD Blu-rays. Skylake had partial support for 10-bit HEVC video, with decoding done by GPU and CPU. With Kaby Lake, this is done entirely in the mfx engine, so that CPU and GPU cores are not used. Videos with high bit rates can therefore be played smoothly, while GPU and CPU cores are not used and therefore use little energy.
To put it to the test, we tried to play a 10-bit video with a resolution of 3840×2160 pixels, encoded with the HEVC codec. The bit rate is extremely high at 400Mbit/s, for comparison, a three-layer UHD Blu-ray has a bit rate of 128Mbit/s. The i7-7500U, as you might expect, had no trouble playing the video. For the Skylake comparison, we tried playing the same video on a desktop system with Core i5-6600K processor. The result was a peak in the CPU load and a video that can be compared to a slideshow. That makes Kaby Lake interesting for people who want to use the CPU in an htpc, although it will have to wait until early 2017 before the desktop processors come on the market.
Preliminary conclusion
It’s difficult to pass judgment on Kaby Lake using the test results of the Zenbook 3 alone. We suspect that the same processor will perform differently in different laptops, due to differences in cooling and power management. In the only benchmark in which these factors play (virtually) no role, Cinebench Single, Kaby Lake at least shows a nice result, although that is not due to architectural improvements, but simply to a higher clock speed. The only real innovation is the full support for decoding 10-bit HEVC video in the mfx, where Skylake was still partly done by the GPU.
Kaby Lake can be summed up with a higher clock speed and an improved mfx. Those aren’t earth-shattering changes and we’ll probably have to wait for Cannon Lake, which is baked at 10nm and should make its appearance at the end of 2017. Until then, we have a slightly smoother sweetener at Kaby Lake.