Intel Kaby Lake Performance: Surprising Jump over Skylake

Introduction

Intel Kaby Lake is already shipping in notebooks, but is the upgrade worth it? More than you might think.

In August at the company’s annual developer forum, Intel officially took the lid off its 7^th 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 7^th 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 6^th Generation Skylake design to the 7^th 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 7^th Gen product deserves more accolades than it is getting.

Architectural Refresher

Before we get into the systems and to our results, I think it’s worth taking some time to quickly go over some of what we know about Kaby Lake from the processor perspective. Most of this content was published back in August just after the Intel Developer Forum, so if you are sure you are caught up, you can jump right along to a pictorial look at the two notebooks being tested today.

At its core, the microarchitecture of Kaby Lake is identical to that of Skylake. Instructions per clock (IPC) remain the same with the exception of dedicated hardware changes in the media engine, so you should not expect any performance differences with Kaby Lake except with improved clock speeds.

Also worth noting is that Intel is still building Kaby Lake on 14nm process technology, the same used on Skylake. The term “same” will be debated as well as Intel claims that improvements made in the process technology over the last 24 months have allowed them to expand clock speeds and improve on efficiency.

Dubbing this new revision of the process as “14nm+”, Intel tells me that they have improved the fin profile for the 3D transistors as well as channel strain while more tightly integrating the design process with manufacturing. The result is a 12% increase in process performance; that is a sizeable gain in a fairly tight time frame even for Intel.

That process improvement directly results in higher clock speeds for Kaby Lake when compared to Skylake when running at the same target TDPs. In general, we are looking at 300-400 MHz higher peak clock speeds in Turbo Boost situations when compared to similar TDP products in the 6th generation. Sustained clocks will very likely remain voltage / thermally limited but the ability spike up to higher clocks for even short bursts can improve performance and responsiveness of Kaby Lake when compared to Skylake.

Along with higher fixed clock speeds for Kaby Lake processors, tweaks to Speed Shift will allow these processors to get to peak clock speeds more quickly than previous designs. I extensively tested Speed Shift when the feature was first enabled in Windows 10 and found that the improvement in user experience was striking. Though the move from Skylake to Kaby Lake won’t be as big of a change, Intel was able to improve the behavior.

The graphics architecture and EU (execution unit) layout remains the same from Skylake, but Intel was able to integrate a new video decode unit to improve power efficiency. That new engine can work in parallel with the EUs to improve performance throughput as well, but obviously at the expensive of some power efficiency.

Specific additions to the codec lineup include decode support for 10-bit HEVC and 8/10-bit VP9 as well as encode support for 10-bit HEVC and 9-bit VP9. The video engine adds HDR support with tone mapping though it does require EU utilization. Wide Color Gamut (Rec. 2020) is prepped and ready to go according to Intel for when that standard starts rolling out to displays.

Performance levels for these new HEVC encode/decode blocks is set to allow for 4K 120mbps real-time on both the Y-series (4.5 watt) and U-series (15 watt) processors.

It’s obvious that the changes to Kaby Lake from Skylake are subtle and even I found myself overlooking the benefits that it might offer. While the capabilities it has will be tested on the desktop side at a later date in 2017, for thin and light notebooks, convertibles and even some tablets, the 7^th Generation Core processors do in fact take advantage of the process improvements and higher clock speeds to offer an improved user experience.