Kaby Lake outperforms Skylake by surprising delta

In a story that I posted over at PC Perspective this week, I took at look at two thin and light convertible notebooks with comparable hardware other than the switch from 6th Generation Core processors (Skylake) to 7th Generation Core processors (Kaby Lake). This latest release from Intel was announced at IDF in August and ends the era of "tick tock" for the company's processor production. Instead of a new process node being implemented with this release, we are seeing a tweaked and perfected 14nm+ process technology that allows Intel to increase clock speeds and add a couple of new features like HEVC / H.265 hardware acceleration.

Here are the some excerpts from the full article over at PC Perspective.

In August at the company’s annual developer forum, Intel officially took the lid off its 7th generation of Core processor series, codenamed Kaby Lake. The build up to this release has been an interesting one as we saw the retirement of the “tick tock” cadence of processor releases and instead are moving into a market where Intel can spend more development time on a single architecture design to refine and tweak it as the engineers see fit. With that knowledge in tow, I believed, as I think many still do today, that Kaby Lake would be something along the lines of a simple rebrand of current shipping product. After all, since we know of no major architectural changes from Skylake other than improvements in the video and media side of the GPU, what is left for us to look forward to?

As it turns out, the advantages of the 7th Generation Core processor family and Kaby Lake are more substantial than I expected. I was able to get a hold of two different notebooks from the HP Spectre lineup, as near to identical as I could manage, with the primary difference being the move from the 6th Generation Skylake design to the 7th Generation Kaby Lake. After running both machines through a gamut of tests ranging from productivity to content creation and of course battery life, I can say with authority that Intel’s 7th Gen product deserves more accolades than it is getting.

The HP Spectre x360 convertible notebook is an impressive machine in your hands. It is built around a 13.3-in 1080p IPS LED backlit display that is multi-touch enabled and has the ability to fold back on itself to convert into a tablet. Our model, the 13-w013dx includes a Core i7-7500U Kaby Lake processor, a 256GB NVMe SSD, 8GB of DDR3 memory as well as 802.11ac wireless.

The HP Spectre x360 with Kaby Lake

The HP Spectre x360 with Kaby Lake

And it’s sexy too – the HP Spectre x360 combines an all metal construction with narrow bezels around the display, an incredibly thin profile and the updated, modern HP logo. When I took this notebook to some meetings on the road, the other media and analysts in the room took notice; not something that you see with modern PCs often.

What follows now is a breakdown of performance of these two notebooks giving us an apples to apples comparison of 6th Generation (Skylake) and 7th Generation (Kaby Lake) Intel mobile processors.

There are two key feature changes that will affect the performance results we captured. The clock speed improvements allowed with the 14nm+ FinFET process technology nets a 200 MHz base frequency improvement and a 400 MHz peak Turbo clock frequency jump. Even though we know that heavy workloads won’t be able to run at peak Turbo speeds indefinitely in thermally constrained environments like notebooks, those speed increases are substantial.

Second, the addition of HEVC (H.265) hardware accelerated decode will offer dramatic decreases in CPU utilization when watching content encoded in that format. As the HEVC codec becomes more popular, even being used in streaming media, this will equate to longer battery life, quieter systems and smooth viewing experiences for media consumption.

The overall performance advantage for the HP Spectre using Kaby Lake is 12.6% while the individual tests range from 10% to 16%. The largest gain is seen on the productivity side, likely due to the bursty nature of the workloads in Excel, etc. Longer workloads will see less of an advantage moving from Skylake simply because the clock speed advantage is less at the base frequencies. For business and consumer usage though, these results point to a noticeable performance increase, a surprise to many.

This is where we start to see the balance of clock speed coming into the results. The 7th Generation Core i7-7500U is able to render the BMW example scene 11% faster than the Core i7-6500U and Gooseberry scene 12% faster. Considering that these have VERY long render times (33 minutes for the BMW test and 250 minutes for the Gooseberry) the results are again more impressive than many will expect. With no IPC improvements on the CPU architecture, these changes are purely in the process technology and platform implementation.

In Rocket League, similar to the result we saw in Sky Diver, the Kaby Lake HD 620 system is 12% faster than the Skylake machine, giving us nearly 60 FPS when running at modest 720p / Quality settings.

Our results in Overwatch give us a 31% improvement in average frame rate when running at 720p and the Medium image quality preset. That number seemed pretty high to me, but I triple ran each test and made sure we were on comparable driver revisions too. It must be a combination of CPU and GPU performance that gives Overwatch the bump in performance, but either way, getting more than 60 FPS in the game on a thin and light convertible notebook is great!

Though the graphics system has the same rated clock window (300 MHz to 1.05 GHz) Intel tells us that with a properly designed thermal system, the operating clock of the GPU portion of Kaby Lake should be consistently higher than that of Skylake.

I honestly wasn’t expecting a result in favor of the Kaby Lake machine by this much. At 10.6 hours of useable web browsing, the newer HP Spectre x360 goes nearly 2 hours longer than last year’s model, an improvement of 22%! (Note: yes, this is a relatively "new" unit of last year's model. Should be no battery wear concerns.)

I should note here that the newer HP Spectre x360 has a 57.9 WHr battery while the previous generation has a 56 WHr battery. Obviously that difference (3%) is not what gives the Kaby Lake system the edge.

Wow! While the new Kaby Lake system was able to playback the movie using less than 10% of the CPU, the Skylake system required ~45% to get the job done. And to be honest, there were some places where I saw dropped frames on Skylake as well – not a perfect viewing experience. It has been a while since we have seen simple video playback hit CPU utilization levels like this.

As you might imagine, this kind of CPU utilization gap will translate to a HUGE amount of battery life advantage for Kaby Lake notebooks while watching similar video. Even upcoming VP9 content being pushed by Google will see this kind of edge on Kaby Lake systems with the dedicated decode block, another capability missing from previous architectures.

Closing Thoughts

What started a simple pet project to get comparable Kaby Lake and Skylake systems in house quickly became a riveting dive into the performance advantages of Intel’s newest architecture. I did not expect the gap between these two most recently platforms to be as wide as it was or as ubiquitous through my testing.

Read the full story at PC Perspective!